Regulatory assembly of the vacuolar proton pump VOV1-ATPase in yeast cells by FLIM-FRET

We investigate the reversible disassembly of VOV1-ATPase in life yeast cells by time resolved confocal FRET imaging. VOV1-ATPase in the vacuolar membrane pumps protons from the cytosol into the vacuole. VOV1-ATPase is a rotary biological nanomotor driven by ATP hydrolysis. The emerging proton gradient is used for transport processes as well as for pH and Ca2+ homoeostasis in the cell. Activity of the VOV1-ATPase is regulated through assembly / disassembly processes. During starvation the two parts of VOV1-ATPase start to disassemble. This process is reversed after addition of glucose. The exact mechanisms are unknown. To follow the disassembly / reassembly in vivo we tagged two subunits C and E with different fluorescent proteins. Cellular distributions of C and E were monitored using a duty cycle-optimized alternating laser excitation scheme (DCO-ALEX) for time resolved confocal FRET-FLIM measurements.Comment: 8 pages, 3 figure

Post-translational modifications in DNA topoisomerase 2α highlight the role of a eukaryote-specific residue in the ATPase domain

Type 2 DNA topoisomerases (Top2) are critical components of key protein complexes involved in DNA replication, chromosome condensation and segregation, as well as gene transcription. The Top2 were found to be the main targets of anticancer agents, leading to intensive efforts to understand their functional and physiological role as well as their molecular structure. Post-translational modifications have been reported to influence Top2 enzyme activities in particular those of the mammalian Top2α isoform. In this study, we identified phosphorylation, and for the first time, acetylation sites in the human Top2α isoform produced in eukaryotic expression systems. Structural analysis revealed that acetylation sites are clustered on the catalytic domains of the homodimer while phosphorylation sites are located in the C-terminal domain responsible for nuclear localization. Biochemical analysis of the eukaryotic-specific K168 residue in the ATPase domain shows that acetylation affects a key position regulating ATP hydrolysis through the modulation of dimerization. Our findings suggest that acetylation of specific sites involved in the allosteric regulation of human Top2 may provide a mechanism for modulation of its catalytic activity.Facultad de Ciencias ExactasInstituto de Física de Líquidos y Sistemas Biológico

Post-translational modifications in DNA topoisomerase 2α highlight the role of a eukaryote-specific residue in the ATPase domain

Type 2 DNA topoisomerases (Top2) are critical components of key protein complexes involved in DNA replication, chromosome condensation and segregation, as well as gene transcription. The Top2 were found to be the main targets of anticancer agents, leading to intensive efforts to understand their functional and physiological role as well as their molecular structure. Post-translational modifications have been reported to influence Top2 enzyme activities in particular those of the mammalian Top2α isoform. In this study, we identified phosphorylation, and for the first time, acetylation sites in the human Top2α isoform produced in eukaryotic expression systems. Structural analysis revealed that acetylation sites are clustered on the catalytic domains of the homodimer while phosphorylation sites are located in the C-terminal domain responsible for nuclear localization. Biochemical analysis of the eukaryotic-specific K168 residue in the ATPase domain shows that acetylation affects a key position regulating ATP hydrolysis through the modulation of dimerization. Our findings suggest that acetylation of specific sites involved in the allosteric regulation of human Top2 may provide a mechanism for modulation of its catalytic activity.Fil: Bedez, Claire. Université de Strasbourg; FranciaFil: Lotz, Christophe. Université de Strasbourg; FranciaFil: Batisse, Claire. Université de Strasbourg; FranciaFil: Broeck, Arnaud Vanden. Université de Strasbourg; FranciaFil: Stote, Roland H.. Université de Strasbourg; FranciaFil: Howard, Eduardo Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Pradeau-Aubreton, Karine. Université de Strasbourg; FranciaFil: Ruff, Marc. Université de Strasbourg; FranciaFil: Lamour, Valérie. Université de Strasbourg; Franci

Purification of Nuclear Poly(A)-binding Protein Nab2 Reveals Association with the Yeast Transcriptome and a Messenger Ribonucleoprotein Core Structure

Nascent mRNAs produced by transcription in the nucleus are subsequently processed and packaged into mRNA ribonucleoprotein particles (messenger ribonucleoproteins (mRNPs)) before export to the cytoplasm. Here, we have used the poly(A)-binding protein Nab2 to isolate mRNPs from yeast under conditions that preserve mRNA integrity. Upon Nab2-tandem affinity purification, several mRNA export factors were co-enriched (Yra1, Mex67, THO-TREX) that were present in mRNPs of different size and mRNA length. High-throughput sequencing of the co-precipitated RNAs indicated that Nab2 is associated with the bulk of yeast transcripts with no specificity for different mRNA classes. Electron microscopy revealed that many of the mRNPs have a characteristic elongated structure. Our data suggest that mRNPs, although associated with different mRNAs, have a unifying core structure

Modular architecture of eukaryotic RNase P and RNase MRP revealed by electron microscopy

Ribonuclease P (RNase P) and RNase MRP are closely related ribonucleoprotein enzymes, which process RNA substrates including tRNA precursors for RNase P and 5.8 S rRNA precursors, as well as some mRNAs, for RNase MRP. The structures of RNase P and RNase MRP have not yet been solved, so it is unclear how the proteins contribute to the structure of the complexes and how substrate specificity is determined. Using electron microscopy and image processing we show that eukaryotic RNase P and RNase MRP have a modular architecture, where proteins stabilize the RNA fold and contribute to cavities, channels and chambers between the modules. Such features are located at strategic positions for substrate recognition by shape and coordination of the cleaved-off sequence. These are also the sites of greatest difference between RNase P and RNase MRP, highlighting the importance of the adaptation of this region to the different substrates

Biochemical and structural characterization of RNases P and MRP in S. cerevisiae

La RNase P est une endoribonucléase responsable de la maturation de l’extrémité 5’ des ARNt prématures. Holoenzyme très conservée, elle est constituée d’une composante ARN formant le noyau catalytique et d’une composante protéique dont le nombre de sous-unités est variable : une protéine chez les bactéries, 5 chez les archées et d’au moins 9 chez les eucaryotes. Les eucaryotes possèdent également une autre endoribonucléase, la RNase MRP dont la composition est proche de la RNase P tant au niveau ribonucléique que protéique mais avec une spécificité de substrat propre. Dans cette étude, nous proposons une méthode originale et spécifique pour purifier la RNase P et la RNase MRP de S. cerevisiae. Grâce à la microscopie électronique et au traitement d’images, nous avons déterminé la première structure de ces deux holoenzymes à une résolution d’environ 1.5 nm. Ces structures révèlent une architecture modulaire commune où les protéines stabilisent la composante ARN et contribuent à l’édification de cavités et de conduits. Les spécificités structurales sont localisées en des positions stratégiques pour l’identification et la coordination du substrat.Ribonuclease P (RNase P) is an endoribonuclease that cleaves the 5'-leader sequence of pre-tRNAs. RNase P is conserved between all taxonomic kingdoms and consists of a catalytic RNA subunit and protein components of variable size, from one protein in bacteria to 5 proteins in archae and at least 9 proteins in eukaryotic cells. In addition to RNase P, eukaryotes possess the RNase MRP which has a related RNA core and shares 8 proteins subunits with RNase P but with its own substrate specificity. Here, we propose an original method to purify specifically RNase P and RNase MRP from S. cerevisiae. Using electron microscopy and image processing, we solved the first structure of these two holoenzymes at a resolution of about 1.5 nm. We showed that eukaryotic RNase P and RNase MRP have a modular architecture, where proteins stabilize the RNA fold and contribute to cavities, channels and chambers between the modules.Structural features are located at strategic positions for substrate recognition by shape and coordination of the cleaved-off sequence

Caractérisation biochimique et structurale des RNases P et MRP chez la levure Saccharomyces cerevisiae

Ribonuclease P (RNase P) is an endoribonuclease that cleaves the 5'-leader sequence of pre-tRNAs. RNase P is conserved between all taxonomic kingdoms and consists of a catalytic RNA subunit and protein components of variable size, from one protein in bacteria to 5 proteins in archae and at least 9 proteins in eukaryotic cells. In addition to RNase P, eukaryotes possess the RNase MRP which has a related RNA core and shares 8 proteins subunits with RNase P but with its own substrate specificity. Here, we propose an original method to purify specifically RNase P and RNase MRP from S. cerevisiae. Using electron microscopy and image processing, we solved the first structure of these two holoenzymes at a resolution of about 1.5 nm. We showed that eukaryotic RNase P and RNase MRP have a modular architecture, where proteins stabilize the RNA fold and contribute to cavities, channels and chambers between the modules.Structural features are located at strategic positions for substrate recognition by shape and coordination of the cleaved-off sequence.La RNase P est une endoribonucléase responsable de la maturation de l’extrémité 5’ des ARNt prématures. Holoenzyme très conservée, elle est constituée d’une composante ARN formant le noyau catalytique et d’une composante protéique dont le nombre de sous-unités est variable : une protéine chez les bactéries, 5 chez les archées et d’au moins 9 chez les eucaryotes. Les eucaryotes possèdent également une autre endoribonucléase, la RNase MRP dont la composition est proche de la RNase P tant au niveau ribonucléique que protéique mais avec une spécificité de substrat propre. Dans cette étude, nous proposons une méthode originale et spécifique pour purifier la RNase P et la RNase MRP de S. cerevisiae. Grâce à la microscopie électronique et au traitement d’images, nous avons déterminé la première structure de ces deux holoenzymes à une résolution d’environ 1.5 nm. Ces structures révèlent une architecture modulaire commune où les protéines stabilisent la composante ARN et contribuent à l’édification de cavités et de conduits. Les spécificités structurales sont localisées en des positions stratégiques pour l’identification et la coordination du substrat

Caractérisation biochimique et structurale des RNases P et MRP chez la levure Saccharomyces cerevisiae

La RNase P est une endoribonucléase responsable de la maturation de l extrémité 5 des ARNt prématures. Holoenzyme très conservée, elle est constituée d une composante ARN formant le noyau catalytique et d une composante protéique dont le nombre de sous-unités est variable : une protéine chez les bactéries, 5 chez les archées et d au moins 9 chez les eucaryotes. Les eucaryotes possèdent également une autre endoribonucléase, la RNase MRP dont la composition est proche de la RNase P tant au niveau ribonucléique que protéique mais avec une spécificité de substrat propre. Dans cette étude, nous proposons une méthode originale et spécifique pour purifier la RNase P et la RNase MRP de S. cerevisiae. Grâce à la microscopie électronique et au traitement d images, nous avons déterminé la première structure de ces deux holoenzymes à une résolution d environ 1.5 nm. Ces structures révèlent une architecture modulaire commune où les protéines stabilisent la composante ARN et contribuent à l édification de cavités et de conduits. Les spécificités structurales sont localisées en des positions stratégiques pour l identification et la coordination du substrat.Ribonuclease P (RNase P) is an endoribonuclease that cleaves the 5'-leader sequence of pre-tRNAs. RNase P is conserved between all taxonomic kingdoms and consists of a catalytic RNA subunit and protein components of variable size, from one protein in bacteria to 5 proteins in archae and at least 9 proteins in eukaryotic cells. In addition to RNase P, eukaryotes possess the RNase MRP which has a related RNA core and shares 8 proteins subunits with RNase P but with its own substrate specificity. Here, we propose an original method to purify specifically RNase P and RNase MRP from S. cerevisiae. Using electron microscopy and image processing, we solved the first structure of these two holoenzymes at a resolution of about 1.5 nm. We showed that eukaryotic RNase P and RNase MRP have a modular architecture, where proteins stabilize the RNA fold and contribute to cavities, channels and chambers between the modules.Structural features are located at strategic positions for substrate recognition by shape and coordination of the cleaved-off sequence.STRASBOURG-Bib.electronique 063 (674829902) / SudocSudocFranceF

Integrase-LEDGF/p75 complex triggers the formation of biomolecular condensates that modulate HIV-1 integration efficiency in vitro

International audienceThe pre-integration steps of the HIV-1 viral cycle are some of the most valuable targets of recent therapeutic innovations. HIV-1 integrase (IN) displays multiple functions, thanks to its considerable conformational flexibility. Recently, such flexible proteins have been characterized by their ability to form biomolecular condensates as a result of Liquid-Liquid-PhaseSeparation (LLPS), allowing them to evolve in a restricted microenvironment within cells called membrane-less organelles (MLO). The LLPS context constitutes a more physiological approach to study the integration of molecular mechanisms performed by intasomes (complexes containing viral DNA, IN, and its cellular cofactor LEDGF/p75). We investigated here if such complexes can form LLPS in vitro andif IN enzymatic activities were affected by this LLPS environment. We observed that the LLPS formed by IN-LEDGF/p75 functional complexes modulate the in vitro IN activities. While the 3' processing of viral DNA ends was drastically reduced inside LLPS, viral DNA strand transfer was strongly enhanced. These two catalytic IN activities appear thus tightly regulated by the environment encountered by intasomes

The kinesin Kif21b regulates radial migration of cortical projection neurons through a non-canonical function on actin cytoskeleton

International audienceCompletion of neuronal migration is critical for brain development. Kif21b is a plus-end-directed kinesin motor protein that promotes intracellular transport and controls microtubule dynamics in neurons. Here we report a physiological function of Kif21b during radial migration of projection neurons in the mouse developing cortex. In vivo analysis in mouse and live imaging on cultured slices demonstrate that Kif21b regulates the radial glia-guided locomotion of newborn neurons independently of its motility on microtubules. We show that Kif21b directly binds and regulates the actin cytoskeleton both in vitro and in vivo in migratory neurons. We establish that Kif21b-mediated regulation of actin cytoskeleton dynamics influences branching and nucleokinesis during neuronal locomotion. Altogether, our results reveal atypical roles of Kif21b on the actin cytoskeleton during migration of cortical projection neurons