Emiliano Ricci

Publications

• 5.15

  Impact points

  The Andes hantavirus NSs protein is expressed from the viral small mRNA by a leaky scanning mechanism.

  Jorge Vera-Otarola, Loretto Solis, Ricardo Soto-Rifo, Emiliano P Ricci, Karla Pino, Nicole D Tischler, Théophile Ohlmann, Jean-Luc Darlix, Marcelo López-Lastra

  Journal of virology. 12/2011; 86(4):2176-87.

  The small mRNA (SmRNA) of all Bunyaviridae encodes the nucleocapsid (N) protein. In 4 out of 5 genera in the Bunyaviridae, the smRNA encodes an additional nonstructural protein denominated NSs. In this study, we show that Andes hantavirus (ANDV) SmRNA encodes an NSs protein. Data show that the NSs p... [more] The small mRNA (SmRNA) of all Bunyaviridae encodes the nucleocapsid (N) protein. In 4 out of 5 genera in the Bunyaviridae, the smRNA encodes an additional nonstructural protein denominated NSs. In this study, we show that Andes hantavirus (ANDV) SmRNA encodes an NSs protein. Data show that the NSs protein is expressed in the context of an ANDV infection. Additionally, our results suggest that translation initiation from the NSs initiation codon is mediated by ribosomal subunits that have bypassed the upstream N protein initiation codon through a leaky scanning mechanism.
• 7.48

  Impact points

  Different effects of the TAR structure on HIV-1 and HIV-2 genomic RNA translation.

  Ricardo Soto-Rifo, Taran Limousin, Paulina S Rubilar, Emiliano P Ricci, Didier Décimo, Olivier Moncorgé, Mary-Anne Trabaud, Patrice André, Andrea Cimarelli, Théophile Ohlmann

  Nucleic acids research. 11/2011;

  The 5'-untranslated region (5'-UTR) of the genomic RNA of human immunodeficiency viruses type-1 (HIV-1) and type-2 (HIV-2) is composed of highly structured RNA motifs essential for viral replication that are expected to interfere with Gag and Gag-Pol translation. Here, we have analyzed and c... [more] The 5'-untranslated region (5'-UTR) of the genomic RNA of human immunodeficiency viruses type-1 (HIV-1) and type-2 (HIV-2) is composed of highly structured RNA motifs essential for viral replication that are expected to interfere with Gag and Gag-Pol translation. Here, we have analyzed and compared the properties by which the viral 5'-UTR drives translation from the genomic RNA of both human immunodeficiency viruses. Our results showed that translation from the HIV-2 gRNA was very poor compared to that of HIV-1. This was rather due to the intrinsic structural motifs in their respective 5'-UTR without involvement of any viral protein. Further investigation pointed to a different role of TAR RNA, which was much inhibitory for HIV-2 translation. Altogether, these data highlight important structural and functional differences between these two human pathogens.
• 7.48

  Impact points

  Activation of a microRNA response in trans reveals a new role for poly(A) in translational repression.

  Emiliano P Ricci, Taran Limousin, Ricardo Soto-Rifo, Rachel Allison, Tuija Pöyry, Didier Decimo, Richard J Jackson, Théophile Ohlmann

  Nucleic acids research. 03/2011; 39(12):5215-31.

  Here, we report that the untreated rabbit reticulocyte lysate contains over 300 different endogenous microRNAs together with the major components of the RNA-induced silencing complex and thus can be used as a model in vitro system to study the effects of microRNAs on gene expression. By using this s... [more] Here, we report that the untreated rabbit reticulocyte lysate contains over 300 different endogenous microRNAs together with the major components of the RNA-induced silencing complex and thus can be used as a model in vitro system to study the effects of microRNAs on gene expression. By using this system, we were able to show that microRNA hybridization to its target resulted in a very rapid and strong inhibition of expression that was exerted exclusively at the level of translation initiation with no involvement of transcript degradation or deadenylation. Moreover, we demonstrate that the magnitude of microRNA-induced repression can only be recapitulated in the context of a competitive translating environment. By using a wide spectrum of competitor cellular and viral RNAs, we could further show that competition was not exerted at the level of general components of the translational machinery, but relied exclusively on the presence of the poly(A) tail with virtually no involvement of the cap structure.
• 5.15

  Impact points

  The 3' untranslated region of the Andes hantavirus small mRNA functionally replaces the poly(A) tail and stimulates cap-dependent translation initiation from the viral mRNA.

  Jorge Vera-Otarola, Ricardo Soto-Rifo, Emiliano P Ricci, Théophile Ohlmann, Jean-Luc Darlix, Marcelo López-Lastra

  Journal of virology. 10/2010; 84(19):10420-4.

  In the process of translation of eukaryotic mRNAs, the 5' cap and the 3' poly(A) tail interact synergistically to stimulate protein synthesis. Unlike its cellular counterparts, the small mRNA (SmRNA) of Andes hantavirus (ANDV), a member of the Bunyaviridae, lacks a 3' poly(A) tail. Here ... [more] In the process of translation of eukaryotic mRNAs, the 5' cap and the 3' poly(A) tail interact synergistically to stimulate protein synthesis. Unlike its cellular counterparts, the small mRNA (SmRNA) of Andes hantavirus (ANDV), a member of the Bunyaviridae, lacks a 3' poly(A) tail. Here we report that the 3' untranslated region (3'UTR) of the ANDV SmRNA functionally replaces a poly(A) tail and synergistically stimulates cap-dependent translation initiation from the viral mRNA. Stimulation of translation by the 3'UTR of the ANDV SmRNA was found to be independent of viral proteins and of host poly(A)-binding protein.
• 4.66

  Impact points

  Structural and Functional diversity of viral IRESes.

  Laurent Balvay, Ricardo Soto-Rifo, Emiliano P Ricci, Didier Decimo, Théophile Ohlmann

  Biochimica et biophysica acta. 08/2009;

  Some 20 years ago, the study of picornaviral RNA translation led to the characterization of an alternative mechanism of initiation by direct ribosome binding to the 5' UTR. By using a bicistronic vector, it was shown that the 5' UTR of the Poliovirus (PV) or the Encephalomyelitis virus (EMCV... [more] Some 20 years ago, the study of picornaviral RNA translation led to the characterization of an alternative mechanism of initiation by direct ribosome binding to the 5' UTR. By using a bicistronic vector, it was shown that the 5' UTR of the Poliovirus (PV) or the Encephalomyelitis virus (EMCV) had the ability to bind the 43 S preinitiation complex in a 5' and cap independent manner. This is rendered possible by an RNA domain called IRES for Internal Ribosome Entry Site which enables efficient translation of a mRNA lacking a 5' cap structure. IRES elements have now been found in many different viral families where they often confer a selective advantage to allow ribosome recruitment under conditions where cap-dependent protein synthesis is severely repressed. In this review, we compare and contrast the structure and function of IRESes that are found within 4 distinct family of RNA positive stranded viruses which are the (i) Picornaviruses; (ii) Flaviviruses; (iii) Dicistroviruses; (iv) Lentiviruses.
• 7.48

  Impact points

  Translation of intronless RNAs is strongly stimulated by the Epstein-Barr virus mRNA export factor EB2.

  Emiliano P Ricci, Fabrice Mure, Henri Gruffat, Didier Decimo, Cahora Medina-Palazon, Théophile Ohlmann, Evelyne Manet

  Nucleic acids research. 07/2009;

  The Epstein-Barr virus protein (EB2) allows the nuclear export of a particular subset of early and late viral RNAs derived from intronless genes. EB2 is conserved among most herpesvirus members and its presence is essential for the production of infectious particles. Here we show that, besides its r... [more] The Epstein-Barr virus protein (EB2) allows the nuclear export of a particular subset of early and late viral RNAs derived from intronless genes. EB2 is conserved among most herpesvirus members and its presence is essential for the production of infectious particles. Here we show that, besides its role as a nuclear export factor, EB2 strongly stimulates translation of unspliced mRNAs without affecting overall cellular translation. Interestingly, this effect can be reversed by the addition of an intron within the gene. The spliced mRNA is then efficiently exported and translated even in the absence of EB2. Moreover, we show that EB2 associates with translating ribosomes and increases the proportion of its target RNA in the polyribosomal fraction. Finally, testing of EB2 homolog proteins derived from EBV-related herpesviruses, shows that, even if they play similar roles within the replication cycle of their respective virus, their mechanisms of action are different.

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• 3.38

  Impact points

  Lentiviral RNAs can use different mechanisms for translation initiation.

  Emiliano P Ricci, Ricardo Soto-Rifo, Cécile H Herbreteau, Didier Decimo, Théophile Ohlmann

  Biochemical Society transactions. 09/2008; 36(Pt 4):690-3.

  The full-length genomic RNA of lentiviruses can be translated to produce proteins and incorporated as genomic RNA in the viral particle. Interestingly, both functions are driven by the genomic 5'-UTR (5'-untranslated region), which harbours structural RNA motifs for the replication cycle of ... [more] The full-length genomic RNA of lentiviruses can be translated to produce proteins and incorporated as genomic RNA in the viral particle. Interestingly, both functions are driven by the genomic 5'-UTR (5'-untranslated region), which harbours structural RNA motifs for the replication cycle of the virus. Recent work has shown that this RNA architecture also functions as an IRES (internal ribosome entry site) in HIV-1 and -2, and in SIV (simian immunodeficiency virus). In addition, the IRES extends to the gag coding region for all these viruses and this leads to the synthesis of shorter isoforms of the Gag polyprotein from downstream initiation codons. In the present study, we have investigated how different members of the lentivirus family (namely HIV-1 and -2, and SIV) can initiate protein synthesis by distinct mechanisms. For this, we have used the competitive reticulocyte lysate that we have recently described. Our results show that HIV-1 is able to drive the synthesis of the Gag polyprotein both by a classical cap-dependent mechanism and an IRES, whereas HIV-2 and SIV appear to use exclusively an IRES mechanism.

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• 5.20

  Impact points

  In vitro expression of the HIV-2 genomic RNA is controlled by three distinct internal ribosome entry segments that are regulated by the HIV protease and the Gag polyprotein.

  Emiliano P Ricci, Cécile H Herbreteau, Didier Decimo, Andreas Schaupp, Siddhartha A K Datta, Alan Rein, Jean-Luc Darlix, Théophile Ohlmann

  RNA (New York, N.Y.). 08/2008; 14(7):1443-55.

  The HIV-2 genomic RNA serves both as a messenger for protein synthesis and as a genome for viral assembly and particle production. Our previous work has shown that the HIV-2 genomic RNA encodes two additional Gag proteins that are N-terminal truncated isoforms of the p57 Gag polyprotein. In this stu... [more] The HIV-2 genomic RNA serves both as a messenger for protein synthesis and as a genome for viral assembly and particle production. Our previous work has shown that the HIV-2 genomic RNA encodes two additional Gag proteins that are N-terminal truncated isoforms of the p57 Gag polyprotein. In this study, by the use of mono- and bicistronic RNAs we show that translation at the three AUGs is driven by three distinct and independent internal ribosome entry segments both in vitro and ex vivo. Furthermore we used the recombinant Gag and HIV-2 protease to show that, in vitro, translation is tightly regulated by these two viral proteins. This regulation is exerted both at the level of protein production and also on the selection of the AUG initiation site which changes the ratio at which the three different Gag isoforms are produced.

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• 7.48

  Impact points

  Back to basics: the untreated rabbit reticulocyte lysate as a competitive system to recapitulate cap/poly(A) synergy and the selective advantage of IRES-driven translation.

  Ricardo Soto-Rifo, Emiliano P Ricci, Didier Décimo, Olivier Moncorgé, Théophile Ohlmann

  Nucleic acids research. 02/2007; 35(18):e121.

  Translation of most eukaryotic mRNAs involves the synergistic action between the 5' cap structure and the 3' poly(A) tail at the initiation step. The poly(A) tail has also been shown to stimulate translation of picornavirus internal ribosome entry sites (IRES)-directed translation. These eff... [more] Translation of most eukaryotic mRNAs involves the synergistic action between the 5' cap structure and the 3' poly(A) tail at the initiation step. The poly(A) tail has also been shown to stimulate translation of picornavirus internal ribosome entry sites (IRES)-directed translation. These effects have been attributed principally to interactions between eIF4G and poly(A)-binding protein (PABP) but also to the participation of PABP in other steps during translation initiation. As the rabbit reticulocyte lysate (RRL) does not recapitulate this cap/poly(A) synergy, several systems based on cellular cell-free extracts have been developed to study the effects of poly(A) tail in vitro but they generally exhibit low translational efficiency. Here, we describe that the non-nuclease-treated RRL (untreated RRL) is able to recapitulate the effects of poly(A) tail on translation in vitro. In this system, translation of a capped/polyadenylated RNA was specifically inhibited by either Paip2 or poly(rA), whereas translation directed by HCV IRES remained unaffected. Moreover, cleavage of eIF4G by FMDV L protease strongly stimulated translation directed by the EMCV IRES, thus recapitulating the competitive advantage that the proteolytic processing of eIF4G confers to IRES-driven RNAs.

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• Structural and functional diversity of viral IRESes

  Laurent Balvay, Ricardo Soto Rifo, Emiliano P. Ricci, Didier Decimo, Théophile Ohlmann

  Biochimica et Biophysica Acta (BBA) - Gene Regulatory Mechanisms.

  Some 20 years ago, the study of picornaviral RNA translation led to the characterization of an alternative mechanism of initiation by direct ribosome binding to the 5′ UTR. By using a bicistronic vector, it was shown that the 5′ UTR of the poliovirus (PV) or the Encephalomyelitis virus (EMCV) had th... [more] Some 20 years ago, the study of picornaviral RNA translation led to the characterization of an alternative mechanism of initiation by direct ribosome binding to the 5′ UTR. By using a bicistronic vector, it was shown that the 5′ UTR of the poliovirus (PV) or the Encephalomyelitis virus (EMCV) had the ability to bind the 43S preinitiation complex in a 5′ and cap-independent manner. This is rendered possible by an RNA domain called IRES for Internal Ribosome Entry Site which enables efficient translation of an mRNA lacking a 5′ cap structure. IRES elements have now been found in many different viral families where they often confer a selective advantage to allow ribosome recruitment under conditions where cap-dependent protein synthesis is severely repressed. In this review, we compare and contrast the structure and function of IRESes that are found within 4 distinct family of RNA positive stranded viruses which are the (i) Picornaviruses; (ii) Flaviviruses; (iii) Dicistroviruses; and (iv) Lentiviruses.