Polyamines as Quality Control Metabolites Operating at the Post-Transcriptional Level

[EN] Plant polyamines (PAs) have been assigned a large number of physiological functions with unknown molecular mechanisms in many cases. Among the most abundant and studied polyamines, two of them, namely spermidine (Spd) and thermospermine (Tspm), share some molecular functions related to quality control pathways for tightly regulated mRNAs at the level of translation. In this review, we focus on the roles of Tspm and Spd to facilitate the translation of mRNAs containing upstream ORFs (uORFs), premature stop codons, and ribosome stalling sequences that may block translation, thus preventing their degradation by quality control mechanisms such as the nonsense-mediated decay pathway and possible interactions with other mRNA quality surveillance pathways.A.F. was funded by the Spanish Ministry of Science, Innovation and Universities, grant number BIO2015-70483-R, and B.B.-P. was funded by the Generalitat Valenciana grant, VALi+d GVA APOSTD/2017/039. D.U. was a recipient of an EMBO short-term fellowship, number STF-7308.Poidevin, L.; Unal, D.; Belda-Palazón, B.; Ferrando Monleón, AR. (2019). Polyamines as Quality Control Metabolites Operating at the Post-Transcriptional Level. Plants. 8(4):1-13. https://doi.org/10.3390/plants8040109S11384Graille, M., & Séraphin, B. (2012). Surveillance pathways rescuing eukaryotic ribosomes lost in translation. Nature Reviews Molecular Cell Biology, 13(11), 727-735. doi:10.1038/nrm3457Preissler, S., & Deuerling, E. (2012). Ribosome-associated chaperones as key players in proteostasis. Trends in Biochemical Sciences, 37(7), 274-283. doi:10.1016/j.tibs.2012.03.002Fuell, C., Elliott, K. A., Hanfrey, C. C., Franceschetti, M., & Michael, A. J. (2010). Polyamine biosynthetic diversity in plants and algae. Plant Physiology and Biochemistry, 48(7), 513-520. doi:10.1016/j.plaphy.2010.02.008Vera-Sirera, F., Minguet, E. G., Singh, S. K., Ljung, K., Tuominen, H., Blázquez, M. A., & Carbonell, J. (2010). Role of polyamines in plant vascular development. Plant Physiology and Biochemistry, 48(7), 534-539. doi:10.1016/j.plaphy.2010.01.011IGARASHI, K., SUGAWARA, K., IZUMI, I., NAGAYAMA, C., & HIROSE, S. (1974). Effect of Polyamines on Polyphenylalanine Synthesis by Escherichia coli and Rat-Liver Ribosomes. European Journal of Biochemistry, 48(2), 495-502. doi:10.1111/j.1432-1033.1974.tb03790.xIGARASHI, K., HASHIMOTO, S., MIYAKE, A., KASHIWAGI, K., & HIROSE, S. (2005). Increase of Fidelity of Polypeptide Synthesis by Spermidine in Eukaryotic Cell-Free Systems. European Journal of Biochemistry, 128(2-3), 597-604. doi:10.1111/j.1432-1033.1982.tb07006.xEchandi, G., & Algranati, I. D. (1975). Defective 30S ribosomal particles in a polyamine auxotroph of Escherichia coli. Biochemical and Biophysical Research Communications, 67(3), 1185-1191. doi:10.1016/0006-291x(75)90798-6Igarashi, K., Kishida, K., & Hirose, S. (1980). Stimulation by polyamines of enzymatic methylation of two adjacent adenines near the 3′ end of 16S ribosomal RNA of Escherichia coli. Biochemical and Biophysical Research Communications, 96(2), 678-684. doi:10.1016/0006-291x(80)91408-4Hetrick, B., Khade, P. K., Lee, K., Stephen, J., Thomas, A., & Joseph, S. (2010). Polyamines Accelerate Codon Recognition by Transfer RNAs on the Ribosome. Biochemistry, 49(33), 7179-7189. doi:10.1021/bi1009776Amarantos, I. (2000). Photoaffinity polyamines: interactions with AcPhe-tRNA free in solution or bound at the P-site of Escherichia coli ribosomes. Nucleic Acids Research, 28(19), 3733-3742. doi:10.1093/nar/28.19.3733Amarantos, I. (2002). The identification of spermine binding sites in 16S rRNA allows interpretation of the spermine effect on ribosomal 30S subunit functions. Nucleic Acids Research, 30(13), 2832-2843. doi:10.1093/nar/gkf404Xaplanteri, M. A. (2005). Localization of spermine binding sites in 23S rRNA by photoaffinity labeling: parsing the spermine contribution to ribosomal 50S subunit functions. Nucleic Acids Research, 33(9), 2792-2805. doi:10.1093/nar/gki557Dever, T. E., & Ivanov, I. P. (2018). Roles of polyamines in translation. Journal of Biological Chemistry, 293(48), 18719-18729. doi:10.1074/jbc.tm118.003338Ivanov, I. P. (2000). Conservation of polyamine regulation by translational frameshifting from yeast to mammals. The EMBO Journal, 19(8), 1907-1917. doi:10.1093/emboj/19.8.1907Brandman, O., & Hegde, R. S. (2016). Ribosome-associated protein quality control. Nature Structural & Molecular Biology, 23(1), 7-15. doi:10.1038/nsmb.3147Behm-Ansmant, I., Kashima, I., Rehwinkel, J., Saulière, J., Wittkopp, N., & Izaurralde, E. (2007). mRNA quality control: An ancient machinery recognizes and degrades mRNAs with nonsense codons. FEBS Letters, 581(15), 2845-2853. doi:10.1016/j.febslet.2007.05.027Chang, Y.-F., Imam, J. S., & Wilkinson, M. F. (2007). The Nonsense-Mediated Decay RNA Surveillance Pathway. Annual Review of Biochemistry, 76(1), 51-74. doi:10.1146/annurev.biochem.76.050106.093909Brogna, S., & Wen, J. (2009). Nonsense-mediated mRNA decay (NMD) mechanisms. Nature Structural & Molecular Biology, 16(2), 107-113. doi:10.1038/nsmb.1550Amrani, N., Sachs, M. S., & Jacobson, A. (2006). Early nonsense: mRNA decay solves a translational problem. Nature Reviews Molecular Cell Biology, 7(6), 415-425. doi:10.1038/nrm1942Rebbapragada, I., & Lykke-Andersen, J. (2009). Execution of nonsense-mediated mRNA decay: what defines a substrate? Current Opinion in Cell Biology, 21(3), 394-402. doi:10.1016/j.ceb.2009.02.007Peccarelli, M., & Kebaara, B. W. (2014). Regulation of Natural mRNAs by the Nonsense-Mediated mRNA Decay Pathway. Eukaryotic Cell, 13(9), 1126-1135. doi:10.1128/ec.00090-14Kurihara, Y., Matsui, A., Hanada, K., Kawashima, M., Ishida, J., Morosawa, T., … Seki, M. (2009). Genome-wide suppression of aberrant mRNA-like noncoding RNAs by NMD in Arabidopsis. Proceedings of the National Academy of Sciences, 106(7), 2453-2458. doi:10.1073/pnas.0808902106Drechsel, G., Kahles, A., Kesarwani, A. K., Stauffer, E., Behr, J., Drewe, P., … Wachter, A. (2013). Nonsense-Mediated Decay of Alternative Precursor mRNA Splicing Variants Is a Major Determinant of the Arabidopsis Steady State Transcriptome. The Plant Cell, 25(10), 3726-3742. doi:10.1105/tpc.113.115485Kalyna, M., Simpson, C. G., Syed, N. H., Lewandowska, D., Marquez, Y., Kusenda, B., … Brown, J. W. S. (2011). Alternative splicing and nonsense-mediated decay modulate expression of important regulatory genes in Arabidopsis. Nucleic Acids Research, 40(6), 2454-2469. doi:10.1093/nar/gkr932Leeds, P., Wood, J. M., Lee, B. S., & Culbertson, M. R. (1992). Gene products that promote mRNA turnover in Saccharomyces cerevisiae. Molecular and Cellular Biology, 12(5), 2165-2177. doi:10.1128/mcb.12.5.2165Kerényi, Z., Mérai, Z., Hiripi, L., Benkovics, A., Gyula, P., Lacomme, C., … Silhavy, D. (2008). Inter-kingdom conservation of mechanism of nonsense-mediated mRNA decay. The EMBO Journal, 27(11), 1585-1595. doi:10.1038/emboj.2008.88Shaul, O. (2015). Unique Aspects of Plant Nonsense-Mediated mRNA Decay. Trends in Plant Science, 20(11), 767-779. doi:10.1016/j.tplants.2015.08.011Rayson, S., Arciga-Reyes, L., Wootton, L., De Torres Zabala, M., Truman, W., Graham, N., … Davies, B. (2012). A Role for Nonsense-Mediated mRNA Decay in Plants: Pathogen Responses Are Induced in Arabidopsis thaliana NMD Mutants. PLoS ONE, 7(2), e31917. doi:10.1371/journal.pone.0031917Shi, C., Baldwin, I. T., & Wu, J. (2012). Arabidopsis Plants Having Defects in Nonsense-mediated mRNA Decay Factors UPF1, UPF2, and UPF3 Show Photoperiod-dependent Phenotypes in Development and Stress Responses. Journal of Integrative Plant Biology, 54(2), 99-114. doi:10.1111/j.1744-7909.2012.01093.xNasim, Z., Fahim, M., & Ahn, J. H. (2017). Possible Role of MADS AFFECTING FLOWERING 3 and B-BOX DOMAIN PROTEIN 19 in Flowering Time Regulation of Arabidopsis Mutants with Defects in Nonsense-Mediated mRNA Decay. Frontiers in Plant Science, 8. doi:10.3389/fpls.2017.00191Degtiar, E., Fridman, A., Gottlieb, D., Vexler, K., Berezin, I., Farhi, R., … Shaul, O. (2015). The feedback control of UPF3 is crucial for RNA surveillance in plants. Nucleic Acids Research, 43(8), 4219-4235. doi:10.1093/nar/gkv237Popp, M. W.-L., & Maquat, L. E. (2013). Organizing Principles of Mammalian Nonsense-Mediated mRNA Decay. Annual Review of Genetics, 47(1), 139-165. doi:10.1146/annurev-genet-111212-133424Dai, Y., Li, W., & An, L. (2015). NMD mechanism and the functions of Upf proteins in plant. Plant Cell Reports, 35(1), 5-15. doi:10.1007/s00299-015-1867-9Karousis, E. D., & Mühlemann, O. (2018). Nonsense-Mediated mRNA Decay Begins Where Translation Ends. Cold Spring Harbor Perspectives in Biology, 11(2), a032862. doi:10.1101/cshperspect.a032862Doma, M. K., & Parker, R. (2006). Endonucleolytic cleavage of eukaryotic mRNAs with stalls in translation elongation. Nature, 440(7083), 561-564. doi:10.1038/nature04530Atkinson, G. C., Baldauf, S. L., & Hauryliuk, V. (2008). Evolution of nonstop, no-go and nonsense-mediated mRNA decay and their termination factor-derived components. BMC Evolutionary Biology, 8(1), 290. doi:10.1186/1471-2148-8-290Szádeczky-Kardoss, I., Gál, L., Auber, A., Taller, J., & Silhavy, D. (2018). The No-go decay system degrades plant mRNAs that contain a long A-stretch in the coding region. Plant Science, 275, 19-27. doi:10.1016/j.plantsci.2018.07.008Shoemaker, C. J., Eyler, D. E., & Green, R. (2010). Dom34:Hbs1 Promotes Subunit Dissociation and Peptidyl-tRNA Drop-Off to Initiate No-Go Decay. Science, 330(6002), 369-372. doi:10.1126/science.1192430Tsuboi, T., Kuroha, K., Kudo, K., Makino, S., Inoue, E., Kashima, I., & Inada, T. (2012). Dom34:Hbs1 Plays a General Role in Quality-Control Systems by Dissociation of a Stalled Ribosome at the 3′ End of Aberrant mRNA. Molecular Cell, 46(4), 518-529. doi:10.1016/j.molcel.2012.03.013Buchan, J. R., & Stansfield, I. (2007). Halting a cellular production line: responses to ribosomal pausing during translation. Biology of the Cell, 99(9), 475-487. doi:10.1042/bc20070037Simms, C. L., Yan, L. L., & Zaher, H. S. (2017). Ribosome Collision Is Critical for Quality Control during No-Go Decay. Molecular Cell, 68(2), 361-373.e5. doi:10.1016/j.molcel.2017.08.019Ozsolak, F., Kapranov, P., Foissac, S., Kim, S. W., Fishilevich, E., Monaghan, A. P., … Milos, P. M. (2010). Comprehensive Polyadenylation Site Maps in Yeast and Human Reveal Pervasive Alternative Polyadenylation. Cell, 143(6), 1018-1029. doi:10.1016/j.cell.2010.11.020Dimitrova, L. N., Kuroha, K., Tatematsu, T., & Inada, T. (2009). Nascent Peptide-dependent Translation Arrest Leads to Not4p-mediated Protein Degradation by the Proteasome. Journal of Biological Chemistry, 284(16), 10343-10352. doi:10.1074/jbc.m808840200Koutmou, K. S., Schuller, A. P., Brunelle, J. L., Radhakrishnan, A., Djuranovic, S., & Green, R. (2015). Ribosomes slide on lysine-encoding homopolymeric A stretches. eLife, 4. doi:10.7554/elife.05534Van Hoof, A., Frischmeyer, P. A., Dietz, H. C., & Parker, R. (2002). Exosome-Mediated Recognition and Degradation of mRNAs Lacking a Termination Codon. Science, 295(5563), 2262-2264. doi:10.1126/science.1067272Frischmeyer, P. A., van Hoof, A., O’Donnell, K., Guerrerio, A. L., Parker, R., & Dietz, H. C. (2002). An mRNA Surveillance Mechanism That Eliminates Transcripts Lacking Termination Codons. Science, 295(5563), 2258-2261. doi:10.1126/science.1067338Szádeczky-Kardoss, I., Csorba, T., Auber, A., Schamberger, A., Nyikó, T., Taller, J., … Silhavy, D. (2018). The nonstop decay and the RNA silencing systems operate cooperatively in plants. Nucleic Acids Research, 46(9), 4632-4648. doi:10.1093/nar/gky279Hanzawa, Y., Takahashi, T., & Komeda, Y. (1997). ACL5: an Arabidopsis gene required for internodal elongation after flowering. The Plant Journal, 12(4), 863-874. doi:10.1046/j.1365-313x.1997.12040863.xHanzawa, Y. (2000). ACAULIS5, an Arabidopsis gene required for stem elongation, encodes a spermine synthase. The EMBO Journal, 19(16), 4248-4256. doi:10.1093/emboj/19.16.4248Knott, J. M., Römer, P., & Sumper, M. (2007). Putative spermine synthases fromThalassiosira pseudonanaandArabidopsis thalianasynthesize thermospermine rather than spermine. FEBS Letters, 581(16), 3081-3086. doi:10.1016/j.febslet.2007.05.074Minguet, E. G., Vera-Sirera, F., Marina, A., Carbonell, J., & Blazquez, M. A. (2008). Evolutionary Diversification in Polyamine Biosynthesis. Molecular Biology and Evolution, 25(10), 2119-2128. doi:10.1093/molbev/msn161Milhinhos, A., Prestele, J., Bollhöner, B., Matos, A., Vera-Sirera, F., Rambla, J. L., … Miguel, C. M. (2013). Thermospermine levels are controlled by an auxin-dependent feedback loop mechanism inPopulusxylem. The Plant Journal, 75(4), 685-698. doi:10.1111/tpj.12231Baima, S., Forte, V., Possenti, M., Peñalosa, A., Leoni, G., Salvi, S., … Morelli, G. (2014). Negative Feedback Regulation of Auxin Signaling by ATHB8/ACL5–BUD2 Transcription Module. Molecular Plant, 7(6), 1006-1025. doi:10.1093/mp/ssu051Kakehi, J. -i., Kuwashiro, Y., Niitsu, M., & Takahashi, T. (2008). Thermospermine is Required for Stem Elongation in Arabidopsis thaliana. Plant and Cell Physiology, 49(9), 1342-1349. doi:10.1093/pcp/pcn109Clay, N. K., & Nelson, T. (2005). Arabidopsis thickvein Mutation Affects Vein Thickness and Organ Vascularization, and Resides in a Provascular Cell-Specific Spermine Synthase Involved in Vein Definition and in Polar Auxin Transport. Plant Physiology, 138(2), 767-777. doi:10.1104/pp.104.055756Muñiz, L., Minguet, E. G., Singh, S. K., Pesquet, E., Vera-Sirera, F., Moreau-Courtois, C. L., … Tuominen, H. (2008). ACAULIS5 controls Arabidopsis xylem specification through the prevention of premature cell death. Development, 135(15), 2573-2582. doi:10.1242/dev.019349Imai, A., Hanzawa, Y., Komura, M., Yamamoto, K. T., Komeda, Y., & Takahashi, T. (2006). The dwarf phenotype of the Arabidopsis acl5 mutant is suppressed by a mutation in an upstream ORF of a bHLH gene. Development, 133(18), 3575-3585. doi:10.1242/dev.02535Imai, A., Komura, M., Kawano, E., Kuwashiro, Y., & Takahashi, T. (2008). A semi-dominant mutation in the ribosomal protein L10 gene suppresses the dwarf phenotype of theacl5mutant inArabidopsis thaliana. The Plant Journal, 56(6), 881-890. doi:10.1111/j.1365-313x.2008.03647.xKakehi, J.-I., Kawano, E., Yoshimoto, K., Cai, Q., Imai, A., & Takahashi, T. (2015). Mutations in Ribosomal Proteins, RPL4 and RACK1, Suppress the Phenotype of a Thermospermine-Deficient Mutant of Arabidopsis thaliana. PLOS ONE, 10(1), e0117309. doi:10.1371/journal.pone.0117309Cai, Q., Fukushima, H., Yamamoto, M., Ishii, N., Sakamoto, T., Kurata, T., … Takahashi, T. (2016). TheSAC51Family Plays a Central Role in Thermospermine Responses in Arabidopsis. Plant and Cell Physiology, 57(8), 1583-1592. doi:10.1093/pcp/pcw113Vera-Sirera, F., De Rybel, B., Úrbez, C., Kouklas, E., Pesquera, M., Álvarez-Mahecha, J. C., … Blázquez, M. A. (2015). A bHLH-Based Feedback Loop Restricts Vascular Cell Proliferation in Plants. Developmental Cell, 35(4), 432-443. doi:10.1016/j.devcel.2015.10.022Yamamoto, M., & Takahashi, T. (2017). Thermospermine enhances translation of SAC51 and SACL1 in Arabidopsis. Plant Signaling & Behavior, 12(1), e1276685. doi:10.1080/15592324.2016.1276685Von Arnim, A. G., Jia, Q., & Vaughn, J. N. (2014). Regulation of plant translation by upstream open reading frames. Plant Science, 214, 1-12. doi:10.1016/j.plantsci.2013.09.006Weiss, M. C., Sousa, F. L., Mrnjavac, N., Neukirchen, S., Roettger, M., Nelson-Sathi, S., & Martin, W. F. (2016). The physiology and habitat of the last universal common ancestor. Nature Microbiology, 1(9). doi:10.1038/nmicrobiol.2016.116Imai, A., Matsuyama, T., Hanzawa, Y., Akiyama, T., Tamaoki, M., Saji, H., … Takahashi, T. (2004). Spermidine Synthase Genes Are Essential for Survival of Arabidopsis. Plant Physiology, 135(3), 1565-1573. doi:10.1104/pp.104.041699Hamasaki-Katagiri, N., Tabor, C. W., & Tabor, H. (1997). Spermidine biosynthesis in Saccharomyces cerevisiae: Polyaminerequirement of a null mutant of the SPE3 gene (spermidine synthase). Gene, 187(1), 35-43. doi:10.1016/s0378-1119(96)00660-9Mandal, S., Mandal, A., Johansson, H. E., Orjalo, A. V., & Park, M. H. (2013). Depletion of cellular polyamines, spermidine and spermine, causes a total arrest in translation and growth in mammalian cells. Proceedings of the National Academy of Sciences, 110(6), 2169-2174. doi:10.1073/pnas.1219002110Park, M. H., & Wolff, E. C. (2018). Hypusine, a polyamine-derived amino acid critical for eukaryotic translation. Journal of Biological Chemistry, 293(48), 18710-18718. doi:10.1074/jbc.tm118.003341Park, M. H. (2006). The Post-Translational Synthesis of a Polyamine-Derived Amino Acid, Hypusine, in the Eukaryotic Translation Initiation Factor 5A (eIF5A). The Journal of Biochemistry, 139(2), 161-169. doi:10.1093/jb/mvj034Chattopadhyay, M. K., Park, M. H., & Tabor, H. (2008). Hypusine modification for growth is the major function of spermidine in Saccharomyces cerevisiae polyamine auxotrophs grown in limiting spermidine. Proceedings of the National Academy of Sciences, 105(18), 6554-6559. doi:10.1073/pnas.0710970105Pällmann, N., Braig, M., Sievert, H., Preukschas, M., Hermans-Borgmeyer, I., Schweizer, M., … Balabanov, S. (2015). Biological Relevance and Therapeutic Potential of the Hypusine Modification System. Journal of Biological Chemistry, 290(30), 18343-18360. doi:10.1074/jbc.m115.664490Nishimura, K., Lee, S. B., Park, J. H., & Park, M. H. (2011). Essential role of eIF5A-1 and deoxyhypusine synthase in mouse embryonic development. Amino Acids, 42(2-3), 703-710. doi:10.1007/s00726-011-0986-zPagnussat, G. C., Yu, H.-J., Ngo, Q. A., Rajani, S., Mayalagu, S., Johnson, C. S., … Sundaresan, V. (2005). Genetic and molecular identification of genes required for female gametophyte development and function inArabidopsis. Development, 132(3), 603-614. doi:10.1242/dev.01595THOMAS, A., GOUMANS, H., AMESZ, H., BENNE, R., & VOORMA, H. O. (1979). A Comparison of the Initiation Factors of Eukaryotic Protein Synthesis from Ribosomes and from the Postribosomal Supernatant. European Journal of Biochemistry, 98(2), 329-337. doi:10.1111/j.1432-1033.1979.tb13192.xCooper, H. L., Park, M. H., Folk, J. E., Safer, B., & Braverman, R. (1983). Identification of the hypusine-containing protein hy+ as translation initiation factor eIF-4D. Proceedings of the National Academy of Sciences, 80(7), 1854-1857. doi:10.1073/pnas.80.7.1854Shiba, T., Mizote, H., Kaneko, T., Nakajima, T., Yasuo, K., & sano, I. (1971). Hypusine, a new amino acid occurring in bovine brain. Biochimica et Biophysica Acta (BBA) - General Subjects, 244(3), 523-531. doi:10.1016/0304-4165(71)90069-9Park, M. H., Cooper, H. L., & Folk, J. E. (1981). Identification of hypusine, an unusual amino acid, in a protein from human lymphocytes and of spermidine as its biosynthetic precursor. Proceedings of the National Academy of Sciences, 78(5), 2869-2873. doi:10.1073/pnas.78.5.2869Saini, P., Eyler, D. E., Green, R., & Dever, T. E. (2009). Hypusine-containing protein eIF5A promotes translation elongation. Nature, 459(7243), 118-121. doi:10.1038/nature08034Schuller, A. P., Wu, C. C.-C., Dever, T. E., Buskirk, A. R., & Green, R. (2017). eIF5A Functions Globally in Translation Elongation and Termination. Molecular Cell, 66(2), 194-205.e5. doi:10.1016/j.molcel.2017.03.003Gäbel, K., Schmitt, J., Schulz, S., Näther, D. J., & Soppa, J. (2013). A Comprehensive Analysis of the Importance of Translation Initiation Factors for Haloferax volcanii Applying Deletion and Conditional Depletion Mutants. PLoS ONE, 8(11), e77188. doi:10.1371/journal.pone.0077188Kyrpides, N. C., & Woese, C. R. (1998). Universally conserved translation initiation factors. Proceedings of the National Academy of Sciences, 95(1), 224-228. doi:10.1073/pnas.95.1.224Navarre, W. W., Zou, S. B., Roy, H., Xie, J. L., Savchenko, A., Singer, A., … Fang, F. C. (2010). PoxA, YjeK, and Elongation Factor P Coordinately Modulate Virulence and Drug Resistance in Salmonella enterica. Molecular Cell, 39(2), 209-221. doi:10.1016/j.molcel.2010.06.021Lassak, J., Keilhauer, E. C., Fürst, M., Wuichet, K., Gödeke, J., Starosta, A. L., … Jung, K. (2015). Arginine-rhamnosylation as new strategy to activate translation elongation factor P. Nature Chemical Biology, 11(4), 266-270. doi:10.1038/nchembio.1751Bullwinkle, T. J., Zou, S. B., Rajkovic, A., Hersch, S. J., Elgamal, S., Robinson, N., … Ibba, M. (2013). (R)-β-Lysine-modified Elongation Factor P Functions in Translation Elongation. Journal of Biological Chemistry, 288(6), 4416-4423. doi:10.1074/jbc.m112.438879Balibar, C. J., Iwanowicz, D., & Dean, C. R. (2013). Elongation Factor P is Dispensable in Escherichia coli and Pseudomonas aeruginosa. Current Microbiology, 67(3), 293-299. doi:10.1007/s00284-013-0363-0Blaha, G., Stanley, R. E., & Steitz, T. A. (2009). Formation of the First Peptide Bond: The Structure of EF-P Bound to the 70 S Ribosome. Science, 325(5943), 966-970. doi:10.1126/science.1175800Melnikov, S., Mailliot, J., Shin, B.-S., Rigger, L., Yusupova, G., Micura, R., … Yusupov, M. (2016). Crystal Structure of Hypusine-Containing Translation Factor eIF5A Bound to a Rotated Eukaryotic Ribosome. Journal of Molecular Biology, 428(18), 3570-3576. doi:10.1016/j.jmb.2016.05.011Schmidt, C., Becker, T., Heuer, A., Braunger, K., Shanmuganathan, V., Pech, M., … Beckmann, R. (2015). Structure of the hypusinylated eukaryotic translation factor eIF-5A bound to the ribosome. Nucleic Acids Research, 44(4), 1944-1951. doi:10.1093/nar/gkv1517Gutierrez, E., Shin, B.-S., Woolstenhulme, C. J., Kim, J.-R., Saini, P., Buskirk, A. R., & Dever, T. E. (2013). eIF5A Promotes Translation of Polyproline Motifs. Molecular Cell, 51(1), 35-45. doi:10.1016/j.molcel.2013.

Relevance of Translational Regulation on Plant Growth and Environmental Responses

The authors acknowledge funding by MINECO BIO2015-70483-R to AF, by CAM S2013/ABI-2734 and by ERC GA260468 to MMC, by the Deutsche Forschungsgemeinschaft (DFG, grant TRR175-C05) to DL, by NSF IOS 1444561 and NSF IOS PAPM-EAGER 1650139 to AS, and by Bio4Energy, a Strategic Research Environment appointed by the Swedish government to JH.Ferrando Monleón, AR.; Castellano, M.; Lisón, P.; Leister, D.; Stepanova, AN.; Hanson, J. (2017). Relevance of Translational Regulation on Plant Growth and Environmental Responses. Frontiers in Plant Science. 8:1-2. https://doi.org/10.3389/fpls.2017.02170S128Hummel, M., Cordewener, J. H. G., de Groot, J. C. M., Smeekens, S., America, A. H. P., & Hanson, J. (2012). Dynamic protein composition of Arabidopsis thaliana cytosolic ribosomes in response to sucrose feeding as revealed by label free MSE proteomics. PROTEOMICS, 12(7), 1024-1038. doi:10.1002/pmic.201100413Vermeulen, S. J., Campbell, B. M., & Ingram, J. S. I. (2012). Climate Change and Food Systems. Annual Review of Environment and Resources, 37(1), 195-222. doi:10.1146/annurev-environ-020411-130608Vogel, C., & Marcotte, E. M. (2012). Insights into the regulation of protein abundance from proteomic and transcriptomic analyses. Nature Reviews Genetics, 13(4), 227-232. doi:10.1038/nrg318

Eukaryotic Initiation Factor 5A2 localizes to actively translating ribosomes to promote cancer cell protrusions and invasive capacity

[EN] Background Eukaryotic Initiation Factor 5A (eIF-5A), an essential translation factor, is post-translationally activated by the polyamine spermidine. Two human genes encode eIF-5A, being eIF5-A1 constitutively expressed whereas eIF5-A2 is frequently found overexpressed in human tumours. The contribution of both isoforms with regard to cellular proliferation and invasion in non-small cell lung cancer remains to be characterized. Methods We have evaluated the use of eIF-5A2 gene as prognosis marker in lung adenocarcinoma (LUAD) patients and validated in immunocompromised mice. We have used cell migration and cell proliferation assays in LUAD lines after silencing each eIF-5A isoform to monitor their contribution to both phenotypes. Cytoskeleton alterations were analysed in the same cells by rhodamine-phalloidin staining and fluorescence microscopy. Polysome profiles were used to monitor the effect of eIF-5A2 overexpression on translation. Western blotting was used to study the levels of eIF-5A2 client proteins involved in migration upon TGFB1 stimulation. Finally, we have co-localized eIF-5A2 with puromycin to visualize the subcellular pattern of actively translating ribosomes. Results We describe the differential functions of both eIF-5A isoforms, to show that eIF5-A2 properties on cell proliferation and migration are coincident with its features as a poor prognosis marker. Silencing of eIF-5A2 leads to more dramatic consequences of cellular proliferation and migration compared to eIF-5A1. Overexpression of eIF5A2 leads to enhanced global translation. We also show that TGF ss signalling enhances the expression and activity of eIF-5A2 which promotes the translation of polyproline rich proteins involved in cytoskeleton and motility features as it is the case of Fibronectin, SNAI1, Ezrin and FHOD1. With the use of puromycin labelling we have co-localized active ribosomes with eIF-5A2 not only in cytosol but also in areas of cellular protrusion. We have shown the bulk invasive capacity of cells overexpressing eIF-5A2 in mice. Conclusions We propose the existence of a coordinated temporal and positional interaction between TFGB and eIF-5A2 pathways to promote cell migration in NSCLC. We suggest that the co-localization of actively translating ribosomes with hypusinated eIF-5A2 facilitates the translation of key proteins not only in the cytosol but also in areas of cellular protrusion.This work was supported by: Fondo de Investigacion Sanitaria, ISCIII, grant number PI20-194, co-funded by ERDF/ESF, "Investing in your future". Ministerio de Educacion, Cultura y Deporte grant FPU13/02755 for JMPS. Asociacion Espanola contra el Cancer, AECC predoctoral grant for AMF. Part of the equipment employed in this work has been funded by Generalitat Valenciana and co-financed with ERDF funds (OP ERDF of Comunitat Valenciana 2014-2020). This article is based upon work from COST Action CA20113 ProteoCure, supported by COST (European Cooperation in Science and Technology).Martínez-Férriz, A.; Gandía, C.; Pardo-Sánchez, JM.; Fathinajafabadi, A.; Ferrando Monleón, AR.; Farras, R. (2023). Eukaryotic Initiation Factor 5A2 localizes to actively translating ribosomes to promote cancer cell protrusions and invasive capacity. Cell Communication and Signaling. 21(1). https://doi.org/10.1186/s12964-023-01076-621

Extremophilic bacteria restrict the growth of Macrophomina phaseolina by combined secretion of polyamines and lytic enzymes

[EN] Extremophilic microorganisms were screened as biocontrol agents against two strains of Macrophomina phaseolina (Mp02 and 06). Stenotrophomonas sp. AG3 and Exiguobacterium sp. S58 exhibited a potential in vitro antifungal effect on Mp02 growth, corresponding to 52.2% and 40.7% inhibition, respectively. This effect was confirmed by scanning electron microscopy, where images revealed marked morphological alterations in fungus hyphae. The bacteria were found to secrete lytic enzymes and polyamines. Exiguobacterium sp. S56a was the only strain able to reduce the growth of the two strains of M. phaseolina through their supernatant. Antifungal supernatant activity was correlated with the ability of bacteria to synthesize and excrete putrescine, and the exogenous application of this polyamine to the medium phenocopied the bacterial antifungal effects. We propose that the combined secretion of putrescine, spermidine, and lytic enzymes by extremophilic microorganism predispose these microorganisms to reduce the disease severity occasioned by M. phaseolina in soybean seedlings.The authors acknowledge the generous financial support by the PICT V Bicentenario 2010 1788 Project (FONCyT, Argentina). This work was performed in the context of a project called ¿Análisis de Adaptación al Cambio Climático en Humedales Andinos¿. ID: 6188775¿8-LP13. Ministerio del Medio Ambiente, Región de Antofagasta. We are also grateful to Lic. C. Pérez Brandan for providing us with the M. phaseolina strains used in this study.Santos, AP.; Nieva Muratore, L.; Sole-Gil, A.; Farías, ME.; Ferrando Monleón, AR.; Blazquez Rodriguez, MA.; Belfiore, C. (2021). Extremophilic bacteria restrict the growth of Macrophomina phaseolina by combined secretion of polyamines and lytic enzymes. Plant Biotechnology Reports. 32:1-9. https://doi.org/10.1016/j.btre.2021.e00674S193

Citrus exocortis viroid causes ribosomal stress in tomato plants

[EN] Viroids are naked RNAs that do not code for any known protein and yet are able to infect plants causing severe diseases. Because of their RNA nature, many studies have focused on the involvement of viroids in RNA-mediated gene silencing as being their pathogenesis mechanism. Here, the alterations caused by the Citrus exocortis viroid (CEVd) on the tomato translation machinery were studied as a new aspect of viroid pathogenesis. The presence of viroids in the ribosomal fractions of infected tomato plants was detected. More precisely, CEVd and its derived viroid small RNAs were found to co-sediment with tomato ribosomes in vivo, and to provoke changes in the global polysome profiles, particularly in the 40S ribosomal subunit accumulation. Additionally, the viroid caused alterations in ribosome biogenesis in the infected tomato plants, affecting the 18S rRNA maturation process. A higher expression level of the ribosomal stress mediator NAC082 was also detected in the CEVd-infected tomato leaves. Both the alterations in the rRNA processing and the induction of NAC082 correlate with the degree of viroid symptomatology. Taken together, these results suggest that CEVd is responsible for defective ribosome biogenesis in tomato, thereby interfering with the translation machinery and, therefore, causing ribosomal stress.Spanish Ministry of Science, Innovation and Universities [BIO2009-11818, BIO2015-70483-R to A.F.]; Spanish Ministry of Science, Innovation and Universities [BFU2009-11958]; Generalitat Valenciana (Valencia, Spain) [AICO/2017/048]; Natural Sciences and Engineering Research Council of Canada [155219-17 to J.-P.P.]; The RNA group is supported by a grant from the Universite de Sherbrooke; J.-P.P. holds the Research Chair of the Universite de Sherbrooke in RNA Structure and Genomics, and is a member of the Centre de Recherche du CHUS; B.B.-P. was a recipient of a VALi+d postdoctoral contract of the Generalitat Valenciana [APOSTD/2017/039]; Schleiff group is funded through the Deutsche Forschungsgemeinschaft [SFB 902]. Funding for open access charge: Spanish Ministry of Science, Innovation and Universities.Cottilli, P.; Belda-Palazón, B.; Adkar-Purushothama, CR.; Perreault, J.; Schleiff, E.; Rodrigo Bravo, I.; Ferrando Monleón, AR.... (2019). Citrus exocortis viroid causes ribosomal stress in tomato plants. Nucleic Acids Research. 47(16):8649-8661. https://doi.org/10.1093/nar/gkz679S86498661471

Fertility and Polarized Cell Growth Depends on eIF5A for Translation of Polyproline-Rich Formins in Saccharomyces cerevisiae

eIF5A is an essential and evolutionary conserved translation elongation factor, which has recently been proposed to be required for the translation of proteins with consecutive prolines. The binding of eIF5A to ribosomes occurs upon its activation by hypusination, a modification that requires spermidine, an essential factor for mammalian fertility that also promotes yeast mating. We show that in response to pheromone, hypusinated eIF5A is required for shmoo formation, localization of polarisome components, induction of cell fusion proteins, and actin assembly in yeast. We also show that eIF5A is required for the translation of Bni1, a proline-rich formin involved in polarized growth during shmoo formation. Our data indicate that translation of the polyproline motifs in Bni1 is eIF5A dependent and this translation dependency is lost upon deletion of the polyprolines. Moreover, an exogenous increase in Bni1 protein levels partially restores the defect in shmoo formation seen in eIF5A mutants. Overall, our results identify eIF5A as a novel and essential regulator of yeast mating through formin translation. Since eIF5A and polyproline formins are conserved across species, our results also suggest that eIF5A-dependent translation of formins could regulate polarized growth in such processes as fertility and cancer in higher eukaryotes.We thank M. E. Perez-Martinez and I. Quilis for their help in viability and beta-galactosidase experiments; J. E. Perez-Ortin for critical reading of the manuscript; and F. Randez-Gil, G. Ammerer, J. Warringer, and S. R. Valentini for materials. We acknowledge funding from the Spanish MCINN (BFU2010-21975-C03-01), the Generalitat Valenciana (PROMETEO 2011/088 and ACOMP/2012/001), Universitat de Valencia (UV-INV-AE13-139034), and support from European Union funds (FEDER). T. L. and B. B.- P. are recipients of a PROMETEO and a VALi+d predoctoral (ACIF2010/085) contract, respectively, from the Generalitat Valenciana.Li, T.; Belda Palazón, B.; Ferrando Monleón, AR.; Alepuz, P. (2014). Fertility and Polarized Cell Growth Depends on eIF5A for Translation of Polyproline-Rich Formins in Saccharomyces cerevisiae. Genetics. 197(4):1191-1200. doi:10.1534/genetics.114.166926S11911200197

Characterization of maize spermine synthase 1 (ZmSPMS1): evidence for dimerization and intracellular location

[EN] Polyamines are ubiquitous positively charged metabolites that play an important role in wide fundamental cellular processes; because of their importance, the homeostasis of these amines is tightly regulated. Spermine synthase catalyzes the formation of polyamine spermine, which is necessary for growth and development in higher eukaryotes. Previously, we reported a stress inducible spermine synthase 1 (ZmSPMS1) gene from maize. The ZmSPMS1 enzyme differs from their dicot orthologous by a C-terminal extension, which contains a degradation PEST sequence involved in its turnover. Herein, we demonstrate that ZmSPMS1 protein interacts with itself in split yeast two-hybrid (Y2H) assays. A Bimolecular Fluorescence Complementation (BiFC) assay revealed that ZmSPMS1 homodimer has a cytoplasmic localization. In order to gain a better understanding about ZmSPMS1 interaction, two deletion constructs of ZmSPMS1 protein were obtained. The Delta N-ZmSPMS1 version, where the first 74 N-terminal amino acids were eliminated, showed reduced capability of dimer formation, whereas the Delta C-ZmSPMS1 version, lacking the last 40 C-terminal residues, dramatically abated the ZmSPMS1-ZmSPMS1 protein interaction. Recombinant protein expression in Escherichia coli of ZmSPMS1 derived versions revealed that deletion of its N-terminal domain affected the spermine biosynthesis, whereas C-terminal ZmSPMS1 truncated version fail to generate this polyamine. These data suggest that N- and C-terminal domains of ZmSPMS1 play a role in a functional homodimer. (C) 2015 Elsevier Masson SAS. All rights reserved.This work was supported by the CONACYT (Investigacion Ciencia Basica CB-2013-221075, Fortalecimiento de infraestructura INFR-2014-01-224800, Renovacion de Infraestructura INFR-2014-01224220) funding to JFJB, and funding from the Spanish MICINN/MINECO (BIO2011-23828) to AF and JC. The authors acknowledge to MC Guillermo Vidriales Escobar from IPICYT for his technical assistance in HPLC analyses.Maruri-López, I.; Hernández-Sánchez, I.; Ferrando Monleón, AR.; Carbonell Gisbert, J.; Jimenez-Bremont, J. (2015). Characterization of maize spermine synthase 1 (ZmSPMS1): evidence for dimerization and intracellular location. Plant Physiology and Biochemistry. 97:264-271. https://doi.org/10.1016/j.plaphy.2015.10.017S2642719

Characterization of Arabidopsis Post-Glycosylphosphatidylinositol Attachment to Proteins Phospholipase 3 Like Genes

[EN] Lipid remodeling of Glycosylphosphatidylinositol (GPI) anchors is required for their maturation and may influence the localization and function of GPI-anchored proteins (GPI-APs). Maturation of GPI-anchors is well characterized in animals and fungi but very little is known about this process in plants. In yeast, the GPI-lipid remodeling occurs entirely at the ER and is initiated by the remodeling enzyme Bst1p (Post-Glycosylphosphatidylinositol Attachment to Proteins inositol deacylase 1 -PGAP1- in mammals and Arabidopsis). Next, the remodeling enzyme Per1p (Post-Glycosylphosphatidylinositol Attachment to Proteins phospholipase 3 -PGAP3- in mammals) removes a short, unsaturated fatty acid of phosphatidylinositol (PI) that is replaced with a very long-chain saturated fatty acid or ceramide to complete lipid remodeling. In mammals, lipid remodeling starts at the ER and is completed at the Golgi apparatus. Studies of the Arabidopsis PGAP1 gene showed that the lipid remodeling of the GPI anchor is critical for the final localization of GPI-APs. Here we characterized loss-of-function mutants of Arabidopsis Per1/PGAP3 like genes (AtPGAP3A and AtPGAP3B). Our results suggest that PGAP3A function is required for the efficient transport of GPI-anchored proteins from the ER to the plasma membrane/cell wall. In addition, loss of function of PGAP3A increases susceptibility to salt and osmotic stresses that may be due to the altered localization of GPI-APs in this mutant. Furthermore, PGAP3B complements a yeast strain lacking PER1 gene suggesting that PGAP3B and Per1p are functional orthologs. Finally, subcellular localization studies suggest that PGAP3A and PGAP3B cycle between the ER and the Golgi apparatus.FA and MM were supported by the Ministerio de Economía y Competitividad (grant no. BFU2016-76607P), Ministerio de Ciencia e Innovación, MICINN/ AEI/10.13039/501100011033 (grant no. PID2020-113847GB-100), and Generalitat Valenciana (AICO/2020/187). CB-S was recipient of a fellowship from Ministerio de Ciencia, Innovación y Universidades (FPU program). CB-S was also recipient of an EMBO short-term fellowship and a short-term fellowship from Ministerio de Ciencia, Innovación y Universidades.Bernat-Silvestre, C.; Ma, Y.; Johnson, K.; Ferrando Monleón, AR.; Aniento, F.; Marcote, MJ. (2022). Characterization of Arabidopsis Post-Glycosylphosphatidylinositol Attachment to Proteins Phospholipase 3 Like Genes. Frontiers in Plant Science. 13:1-15. https://doi.org/10.3389/fpls.2022.8179151151

Polyamines interfere with protein ubiquitylation and cause depletion of intracellular amino acids: a possible mechanism for cell growth inhibition

[EN] Spermidine is a polyamine present in eukaryotes with essential functions in protein synthesis. At high concentrations spermidine and norspermidine inhibit growth by unknown mechanisms. Transcriptomic analysis of the effect of norspermidine on the plant Arabidopsis thaliana indicates upregulation of the response to heat stress and denatured proteins. Accordingly, these polyamines inhibit protein ubiquitylation, both in vivo (in yeast, Arabidopsis, and human Hela cells) and in vitro (with recombinant ubiquitin ligase). This interferes with protein degradation by the proteasome, a situation known to deplete cells of amino acids. Norspermidine treatment of yeast cells induces amino acid depletion, and supplementation of media with amino acids counteracts growth inhibition and cellular amino acid depletion but not inhibition of protein polyubiquitylation.This work was supported by grant PROMETEO II 2014/041 from Generalitat Valenciana, Valencia, Spain.Sayas Montañana, EM.; Pérez-Benavente, B.; Manzano, C.; Farràs, R.; Alejandro Martinez, S.; Del Pozo, J.; Ferrando Monleón, AR.... (2019). Polyamines interfere with protein ubiquitylation and cause depletion of intracellular amino acids: a possible mechanism for cell growth inhibition. FEBS Letters. 593(2):209-218. https://doi.org/10.1002/1873-3468.13299S2092185932Yoda, H., Fujimura, K., Takahashi, H., Munemura, I., Uchimiya, H., & Sano, H. (2009). Polyamines as a common source of hydrogen peroxide in host- and nonhost hypersensitive response during pathogen infection. Plant Molecular Biology, 70(1-2), 103-112. doi:10.1007/s11103-009-9459-0Pérez-Benavente, B., & Farràs, R. (2016). Cell Synchronization Techniques to Study the Action of CDK Inhibitors. Cyclin-Dependent Kinase (CDK) Inhibitors, 85-93. doi:10.1007/978-1-4939-2926-9_8Bissoli, G., Niñoles, R., Fresquet, S., Palombieri, S., Bueso, E., Rubio, L., … Serrano, R. (2012). Peptidyl-prolyl cis-trans isomerase ROF2 modulates intracellular pH homeostasis in Arabidopsis. The Plant Journal, 70(4), 704-716. doi:10.1111/j.1365-313x.2012.04921.xGuerra, D., Mastrangelo, A. M., Lopez-Torrejon, G., Marzin, S., Schweizer, P., Stanca, A. M., … Mazzucotelli, E. (2011). Identification of a Protein Network Interacting with TdRF1, a Wheat RING Ubiquitin Ligase with a Protective Role against Cellular Dehydration. Plant Physiology, 158(2), 777-789. doi:10.1104/pp.111.183988Bueso, E., Ibañez, C., Sayas, E., Muñoz-Bertomeu, J., Gonzalez-Guzmán, M., Rodriguez, P. L., & Serrano, R. (2014). A forward genetic approach in Arabidopsis thaliana identifies a RING-type ubiquitin ligase as a novel determinant of seed longevity. Plant Science, 215-216, 110-116. doi:10.1016/j.plantsci.2013.11.004Nodzon, L. A., Xu, W.-H., Wang, Y., Pi, L.-Y., Chakrabarty, P. K., & Song, W.-Y. (2004). The ubiquitin ligase XBAT32 regulates lateral root development in Arabidopsis. The Plant Journal, 40(6), 996-1006. doi:10.1111/j.1365-313x.2004.02266.xDobson, C. M. (2003). Protein folding and misfolding. Nature, 426(6968), 884-890. doi:10.1038/nature02261Trotter, E. W., Kao, C. M.-F., Berenfeld, L., Botstein, D., Petsko, G. A., & Gray, J. V. (2002). Misfolded Proteins Are Competent to Mediate a Subset of the Responses to Heat Shock in Saccharomyces cerevisiae. Journal of Biological Chemistry, 277(47), 44817-44825. doi:10.1074/jbc.m204686200Sugio, A., Dreos, R., Aparicio, F., & Maule, A. J. (2009). The Cytosolic Protein Response as a Subcomponent of the Wider Heat Shock Response in Arabidopsis. The Plant Cell, 21(2), 642-654. doi:10.1105/tpc.108.062596Ciechanover, A. (1998). The ubiquitin-proteasome pathway: on protein death and cell life. The EMBO Journal, 17(24), 7151-7160. doi:10.1093/emboj/17.24.7151Vierstra, R. D. (2009). The ubiquitin–26S proteasome system at the nexus of plant biology. Nature Reviews Molecular Cell Biology, 10(6), 385-397. doi:10.1038/nrm2688Kisselev, A. F., & Goldberg, A. L. (2001). Proteasome inhibitors: from research tools to drug candidates. Chemistry & Biology, 8(8), 739-758. doi:10.1016/s1074-5521(01)00056-4Wenzel, D. M., Lissounov, A., Brzovic, P. S., & Klevit, R. E. (2011). UBCH7 reactivity profile reveals parkin and HHARI to be RING/HECT hybrids. Nature, 474(7349), 105-108. doi:10.1038/nature09966Lee, D. H., & Goldberg, A. L. (1998). Proteasome inhibitors: valuable new tools for cell biologists. Trends in Cell Biology, 8(10), 397-403. doi:10.1016/s0962-8924(98)01346-4Zhang, W., & Sidhu, S. S. (2013). Development of inhibitors in the ubiquitination cascade. FEBS Letters, 588(2), 356-367. doi:10.1016/j.febslet.2013.11.003De Lucas, M., & Prat, S. (2014). PIFs get BRright: PHYTOCHROME INTERACTING FACTORs as integrators of light and hormonal signals. New Phytologist, 202(4), 1126-1141. doi:10.1111/nph.12725Hedden, P., & Sponsel, V. (2015). A Century of Gibberellin Research. Journal of Plant Growth Regulation, 34(4), 740-760. doi:10.1007/s00344-015-9546-1McClellan, A. J., Scott, M. D., & Frydman, J. (2005). Folding and Quality Control of the VHL Tumor Suppressor Proceed through Distinct Chaperone Pathways. Cell, 121(5), 739-748. doi:10.1016/j.cell.2005.03.024Schwartz, A. L., & Ciechanover, A. (2009). Targeting Proteins for Destruction by the Ubiquitin System: Implications for Human Pathobiology. Annual Review of Pharmacology and Toxicology, 49(1), 73-96. doi:10.1146/annurev.pharmtox.051208.165340Suraweera, A., Münch, C., Hanssum, A., & Bertolotti, A. (2012). Failure of Amino Acid Homeostasis Causes Cell Death following Proteasome Inhibition. Molecular Cell, 48(2), 242-253. doi:10.1016/j.molcel.2012.08.003Hinnebusch, A. G. (2005). TRANSLATIONAL REGULATION OFGCN4AND THE GENERAL AMINO ACID CONTROL OF YEAST. Annual Review of Microbiology, 59(1), 407-450. doi:10.1146/annurev.micro.59.031805.133833Albert, V., & Hall, M. N. (2015). mTOR signaling in cellular and organismal energetics. Current Opinion in Cell Biology, 33, 55-66. doi:10.1016/j.ceb.2014.12.001Arruabarrena-Aristorena, A., Zabala-Letona, A., & Carracedo, A. (2018). Oil for the cancer engine: The cross-talk between oncogenic signaling and polyamine metabolism. Science Advances, 4(1), eaar2606. doi:10.1126/sciadv.aar260