Schlafen 12 restricts HIV-1 latency reversal by a codon-usage dependent post-transcriptional block in CD4+ T cells

Latency is a major barrier towards virus elimination in HIV-1-infected individuals. Yet, the mechanisms that contribute to the maintenance of HIV-1 latency are incompletely understood. Here we describe the Schlafen 12 protein (SLFN12) as an HIV-1 restriction factor that establishes a post-transcriptional block in HIV-1-infected cells and thereby inhibits HIV-1 replication and virus reactivation from latently infected cells. The inhibitory activity is dependent on the HIV-1 codon usage and on the SLFN12 RNase active sites. Within HIV-1-infected individuals, SLFN12 expression in PBMCs correlated with HIV-1 plasma viral loads and proviral loads suggesting a link with the general activation of the immune system. Using an RNA FISH-Flow HIV-1 reactivation assay, we demonstrate that SLFN12 expression is enriched in infected cells positive for HIV-1 transcripts but negative for HIV-1 proteins. Thus, codon-usage dependent translation inhibition of HIV-1 proteins participates in HIV-1 latency and can restrict the amount of virus release after latency reversal. In cell lines and HIV-1 patient PBMCs, the Schlafen 12 protein (SLFN12) is shown to be an HIV-1 restriction factor that inhibits HIV-1 replication and virus reactivatio

Schlafen 12 restricts HIV-1 latency reversal by a codon-usage dependent post-transcriptional block in CD4+ T cells

Latency is a major barrier towards virus elimination in HIV-1-infected individuals. Yet, the mechanisms that contribute to the maintenance of HIV-1 latency are incompletely understood. Here we describe the Schlafen 12 protein (SLFN12) as an HIV-1 restriction factor that establishes a post-transcriptional block in HIV-1-infected cells and thereby inhibits HIV-1 replication and virus reactivation from latently infected cells. The inhibitory activity is dependent on the HIV-1 codon usage and on the SLFN12 RNase active sites. Within HIV-1-infected individuals, SLFN12 expression in PBMCs correlated with HIV-1 plasma viral loads and proviral loads suggesting a link with the general activation of the immune system. Using an RNA FISH-Flow HIV-1 reactivation assay, we demonstrate that SLFN12 expression is enriched in infected cells positive for HIV-1 transcripts but negative for HIV-1 proteins. Thus, codon-usage dependent translation inhibition of HIV-1 proteins participates in HIV-1 latency and can restrict the amount of virus release after latency reversal.We thank Drs Yingying Li, Feng Gao and Beatrice H. Hahn for providing codon-optimized HIV-1 Gag expression vector, Drs James Hoxie and Susan Zolla-Pazner for supplying anti-Nef and -p24 antibodies, respectively through the NIH AIDS reagent program. We also thank Dr Song Gao for providing SLFN13-tRNA structure information, and Dr Maria-Eugenia Gas Lopez and Dr Ester Gea-Mallorquí for advise. This work was supported by following grants: M.K.I., JSPS Oversea Research Fellowship and Takeda Science Foundation; A.E.C., PT17/0009/0019 (ISCIII/MINECO and FEDER); M.J.B., RTI2018-101082-B-I00 and PID2021-123321OB-I00 [MINECO/FEDER]), and the Miguel Servet program by ISCIII (CP17/00179 and CPII22/00005); C.B., M.R.R., C.D.C., European Union’s Horizon 2020 research and innovation program under grant agreement 681137-EAVI2020 and NIH grant P01-AI131568; J.D., the Spanish Ministry of Science and Innovation (PID2019106959RB-I00/AEI/10.13039/501100011033); A.M., the Spanish Ministry of Science and Innovation (PID2019-106323RB-I00 AEI//10.13039/501100011033) and the institutional “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000792-M).info:eu-repo/semantics/publishedVersio

Unraveling novel roles of the cellular decapping activators Lsm1-7 and Dhh1 in translation control through viral studies

Translation control is a vital aspect of gene expression for both viruses and their cellular hosts. We have previously shown that the cellular mRNA decay activators Dhh1 and Lsm1-7 promote translation of positive-strand RNA [(+)RNA] viral genomes and their subsequent transport from the cellular translation machinery to replication complexes, a process that requires translation repression. These key steps in the replication of all (+)RNA viruses require profound rearrangements of the viral ribonucleoprotein (RNP) composition. How cellular decapping activators promote translation and replication of viral genomes remains unknown. Using the replication of the Brome mosaic virus in yeast, a fruitful model system for (+)RNA viral replication, we show that Dhh1 and Lsm1-7 function differentially in viral RNA translation and replication by assembling alternative mRNP complexes. The dependence on Dhh1 for viral RNA translation initiation is mediated by specific cis-acting sequences in the viral UTRs and a stem-loop in the ORF. Excitingly, by ribosome profiling analyses we identify a specific subset of cellular mRNAs that also depends on Dhh1 for translation. These mRNAs have as (+)RNA genomes long 5´UTR and highly structured 5´UTRs and ORFs. Moreover, they are enriched in mRNAs related to ribosome biogenesis. Interestingly, ribosome biogenesis is often altered in cancer cells and we and others determine that DDX6, the human ortholog of Dhh1, is indeed overexpressed in pancreatic and colon cancer. In conclusion, our results demonstrate that components of the cellular decapping machinery have a broad function in translational regulation. This enables fast fine-tuning of gene expression in response to perturbations.El control de la traducción es un aspecto vital de la expresión génica tanto para los virus como para sus huéspedes celulares. Nuestro laboratorio ha demostrado que los activadores de la degradación del ARN mensajero celular, Dhh1 y Lsm1-7, promueven la traducción de los genomas de virus de ARN de cadena sencilla y polaridad positiva [(+)ARN] así como su transporte desde la maquinaria de traducción celular a los complejos de replicación, un proceso que necesita represión de la traducción. Estos pasos clave en la replicación de todos los virus (+)ARN requieren de una profunda reorganización en la composición de la ribonucleoproteina (RNP) viral. Cómo los activadores del decapping celular promueven la traducción y replicación de los genomas virales aún es desconocido. Utilizando la replicación del virus del mosaico del Bromus en levadura, un modelo muy usado para el estudio de la replicación de virus (+)ARN, hemos demostrado que Dhh1 y Lsm1-7 funcionan de manera distinta en la traducción y replicación del ARN viral mediante el ensamblaje de complejos alternativos de RNP. La dependencia de Dhh1 para la iniciación de la traducción del ARN viral está mediada por secuencias específicas cis-acting localizadas en las regiones no traducidas (RNTs) del virus y un stem-loop en el marco de lectura. Sorprendentemente, mediante el uso del ribosome profiling hemos identificado un grupo específico de ARN mensajeros celulares que también dependen de Dhh1 para su traducción. Estos ARN mensajeros tienen, como los genomas de los virus (+)ARN, 5’RNT largos y altamente estructurados, así como marcos de lectura altamente estructurados. Además, entre ellos abundan los ARN mensajeros relacionados con biogénesis ribosomal. Es interesante mencionar que la biogénesis ribosomal está normalmente alterada en células cancerosas y nosotros, y otros grupos, hemos determinado que DDX6, el ortólogo en humanos de Dhh1, está sobreexpresado en cáncer pancreático y de colon. En conclusión, nuestros resultados demuestran que componentes de la maquinaria de decapping celular tienen una amplia función en la regulación de la traducción. Este hecho permite un rápido y preciso ajuste de la expresión génica en respuesta a perturbaciones

Translation control: Learning from viruses, again

Viruses are powerful tools to uncover cellular processes. Through viral studies we have recently identified a novel translational control mechanism that involves the DEAD-box helicase Dhh1/DDX6 and RNA folding within coding sequences (CDSs). All Dhh1-dependent mRNAs, viral and cellular ones, (i) contain long and highly structured CDSs, (ii) are directly bound by Dhh1 with a specific pattern, (iii) are activated at the translation initiation step and (iv) express proteins associated with the endoplasmic reticulum. The obtained results uncover a novel layer of translation regulation associated with translation at the endoplasmic reticulum conserved from yeast to humans and hijacked by viruses.This work was supported by the Spanish Ministry of Economy and Competitiveness through grant BFU2016–80039-R (AEI/MINEICO/FEDER, UE) and the “Maria de Maeztu” Program for Units of Excellence in R&D (MDM-2014–0370)

Translation control: Learning from viruses, again

Viruses are powerful tools to uncover cellular processes. Through viral studies we have recently identified a novel translational control mechanism that involves the DEAD-box helicase Dhh1/DDX6 and RNA folding within coding sequences (CDSs). All Dhh1-dependent mRNAs, viral and cellular ones, (i) contain long and highly structured CDSs, (ii) are directly bound by Dhh1 with a specific pattern, (iii) are activated at the translation initiation step and (iv) express proteins associated with the endoplasmic reticulum. The obtained results uncover a novel layer of translation regulation associated with translation at the endoplasmic reticulum conserved from yeast to humans and hijacked by viruses.This work was supported by the Spanish Ministry of Economy and Competitiveness through grant BFU2016–80039-R (AEI/MINEICO/FEDER, UE) and the “Maria de Maeztu” Program for Units of Excellence in R&D (MDM-2014–0370)

Use of cellular decapping activators by positive-strand RNA viruses

Positive-strand RNA viruses have evolved multiple strategies to not only circumvent the hostile decay machinery but to trick it into being a priceless collaborator supporting viral RNA translation and replication. In this review, we describe the versatile interaction of positive-strand RNA viruses and the 5'-3' mRNA decay machinery with a focus on the viral subversion of decapping activators. This highly conserved viral trickery is exemplified with the plant Brome mosaic virus, the animal Flock house virus and the human hepatitis C virus.This work was supported by the Spanish Ministry of Economy and Competitiveness through/ngrant BFU 2013-44629-R and the “Maria de Maeztu” Programme for Units of Excellence in R&D (MDM-2014-0370

The Lsm1-7-Pat1 complex promotes viral RNA translation and replication by differential mechanisms

The Lsm1-7-Pat1 complex binds to the 3' end of cellular mRNAs and promotes 3' end protection and 5'-3' decay. Interestingly, this complex also specifically binds to cis-acting regulatory sequences of viral positive-strand RNA genomes promoting their translation and subsequent recruitment from translation to replication. Yet, how the Lsm1-7-Pat1 complex regulates these two processes remains elusive. Here, we show that Lsm1-7-Pat1 complex acts differentially in these processes. By using a collection of well-characterized lsm1 mutant alleles and a system that allows the replication of Brome mosaic virus (BMV) in yeast we show that the Lsm1-7-Pat1 complex integrity is essential for both, translation and recruitment. However, the intrinsic RNA-binding ability of the complex is only required for translation. Consistent with an RNA-binding-independent function of the Lsm1-7-Pat1 complex on BMV RNA recruitment, we show that the BMV 1a protein, the sole viral protein required for recruitment, interacts with this complex in an RNA-independent manner. Together, these results support a model wherein Lsm1-7-Pat1 complex binds consecutively to BMV RNA regulatory sequences and the 1a protein to promote viral RNA translation and later recruitment out of the host translation machinery to the viral replication complexes.This work was supported by a grant from the Spanish Ministerio de Ciencia e Innovación (BFU2013-44629-R) and USUHS intramural grant to S.T. J.J. was supported by grant 2012FI_B00574 from the Generalitat de Catalunya

The Lsm1-7-Pat1 complex promotes viral RNA translation and replication by differential mechanisms

The Lsm1-7-Pat1 complex binds to the 3' end of cellular mRNAs and promotes 3' end protection and 5'-3' decay. Interestingly, this complex also specifically binds to cis-acting regulatory sequences of viral positive-strand RNA genomes promoting their translation and subsequent recruitment from translation to replication. Yet, how the Lsm1-7-Pat1 complex regulates these two processes remains elusive. Here, we show that Lsm1-7-Pat1 complex acts differentially in these processes. By using a collection of well-characterized lsm1 mutant alleles and a system that allows the replication of Brome mosaic virus (BMV) in yeast we show that the Lsm1-7-Pat1 complex integrity is essential for both, translation and recruitment. However, the intrinsic RNA-binding ability of the complex is only required for translation. Consistent with an RNA-binding-independent function of the Lsm1-7-Pat1 complex on BMV RNA recruitment, we show that the BMV 1a protein, the sole viral protein required for recruitment, interacts with this complex in an RNA-independent manner. Together, these results support a model wherein Lsm1-7-Pat1 complex binds consecutively to BMV RNA regulatory sequences and the 1a protein to promote viral RNA translation and later recruitment out of the host translation machinery to the viral replication complexes.This work was supported by a grant from the Spanish Ministerio de Ciencia e Innovación (BFU2013-44629-R) and USUHS intramural grant to S.T. J.J. was supported by grant 2012FI_B00574 from the Generalitat de Catalunya

CHIKV infection reprograms codon optimality to favor viral RNA translation by altering the tRNA epitranscriptome

Ample evidence indicates that codon usage bias regulates gene expression. How viruses, such as the emerging mosquito-borne Chikungunya virus (CHIKV), express their genomes at high levels despite an enrichment in rare codons remains a puzzling question. Using ribosome footprinting, we analyze translational changes that occur upon CHIKV infection. We show that CHIKV infection induces codon-specific reprogramming of the host translation machinery to favor the translation of viral RNA genomes over host mRNAs with an otherwise optimal codon usage. This reprogramming was mostly apparent at the endoplasmic reticulum, where CHIKV RNAs show high ribosome occupancy. Mechanistically, it involves CHIKV-induced overexpression of KIAA1456, an enzyme that modifies the wobble U34 position in the anticodon of tRNAs, which is required for proper decoding of codons that are highly enriched in CHIKV RNAs. Our findings demonstrate an unprecedented interplay of viruses with the host tRNA epitranscriptome to adapt the host translation machinery to viral production.This work was supported by the Spanish Ministry of Science and Innovation (PID2019-106959RB-I00/AEI/10.13039/501100011033 and PCIN-2016-106 to JD and PGC2018-098152-A-100 to EMN) and by an institutional “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000792-M) and by the 2017 SGR 909 grant from the Secretaria d’Universitats i Recerca del Departament d’Economia i Coneixement de la Generalitat de Catalunya. RB was a recipient of a Juan de la Cierva fellowship. Mass spectrometric analyses were performed in the CRG/UPF Proteomics Unit (Proteored, PRB3, grant PT17/0019 PE I + D + i 2013-2016, ISCIII and ERDF). We thank C. V. Nicchitta and S. Leidel for experimental advice and F. Gebauer and A. Meyerhans for fruitful discussions. We acknowledge the support of the MEIC to the EMBL partnership, Centro de Excelencia Severo Ochoa and CERCA Programme/Generalitat de Catalunya

A mathematical model of rna3 recruitment in the replication cycle of brome mosaic virus

Positive-strand RNA viruses, such as the brome mosaic virus (BMV) and hepatitis C virus, utilize a replication cycle which involves the recruitment of RNA genomes from the cellular translation machinery to the viral replication complexes. Here, we coupled mathematical modeling with a statistical inverse problem methodology to better understand this crucial recruitment process. We developed a discrete-delay differential equation model that describes the production of BMV protein 1a and BMV RNA3, and the effect of protein 1a on RNA3 recruitment. We validated our model with experimental data generated in duplicate from a yeast strain that was engineered to express protein 1a and RNA3 under the control of inducible promoters. We used a statistical model comparison technique to test which biological assumptions in our model were correct. Our results suggest that protein 1a expression is governed by a nonlinear phenomenon and that a time delay is important for modeling RNA3 recruitment. We also performed an uncertainty analysis of two experimental designs and found that we could improve our data collection procedure in future experiments to increase the confidence in our parameter estimates.This research was supported in part by grant number NIAID R01 AI071915-09 from the National Institute of Allergy and Infectious Diseases, in part by the Undergraduate Biomathematics grant number NSF DBI-1129214 from the National Science Foundation and in part by a grant from the Spanish Ministerio de Ciencia e Innovación (BFU2010-2008