Formation of large viroplasms and virulence of Cauliflower mosaic virus in turnip plants depend on the N-terminal EKI sequence of viral protein TAV

International audienc

Strength in Diversity: Nuclear Export of Viral RNAs

International audienc

Study of Cauliflower Mosaic Virus (CaMV) mRNAs nuclear export in Arabidopsis thaliana

Chez les métazoaires et leurs virus la majorité des ARNm est exportée du noyau par les exportines TAP-p15 et le complexe TREX-1, alors qu’une minorité est exportée par CRM1. Chez les plantes ce processus fondamental reste peu décrit voir inconnu pour les phytovirus comme le CaMV et ses ARNm 19S et 35S. Notre objectif a été de clarifier cette étape primordiale mais jamais étudiée du cycle de CaMV et de l'utiliser pour mieux comprendre l'export nucléaire des ARNm chez la plante modèle Arabidopsis thaliana. Nos principaux résultats montrent que le CaMV utilise les deux voies d’export, celle de TREX-1 et celle de CRM1, pour exporter ses ARN 35S et que le précurseur de sa protéase et transcriptase inverse, P5, est important pour l’export par TREX-1. Nous avons également démontré que la région leader de ces ARN viraux, et en particulier sa structure secondaire, est un élément reconnu par la machinerie d’export nucléaire.In metazoa most of the mature cellular and viral mRNAs are exported out of the nucleus via the TAP-p15 export receptors and their associated TREX-1 complex while a minority is exported by the exportin CRM1. In plants, this fundamental process is poorly known and even unknown for DNA phytoviruses such as CaMV and its 19S and 35S mRNAs. Our aim was to clarify this important but never studied step in CaMV life cycle in order to decode the mechanisms of mRNAs nuclear export in the model plant Arabidopsis thaliana. Our main results show that CaMV uses both the TREX-1 complex pathway as well as CRM1 to export its 35S mRNAs, and that the precursor of the viral proteinase and retrotranscriptase, P5, is important for the nuclear export by TREX-1. We also demonstrated that CaMV 35S RNA leader region and especially its highly structured stem-loop is a cis-acting element recognized by the mRNAs nuclear export machinery

Étude de l'export nucléaire des ARNm du virus de la mosaïque du chou-fleur (CaMV) chez Arabidopsis thaliana

In metazoa most of the mature cellular and viral mRNAs are exported out of the nucleus via the TAP-p15 export receptors and their associated TREX-1 complex while a minority is exported by the exportin CRM1. In plants, this fundamental process is poorly known and even unknown for DNA phytoviruses such as CaMV and its 19S and 35S mRNAs. Our aim was to clarify this important but never studied step in CaMV life cycle in order to decode the mechanisms of mRNAs nuclear export in the model plant Arabidopsis thaliana. Our main results show that CaMV uses both the TREX-1 complex pathway as well as CRM1 to export its 35S mRNAs, and that the precursor of the viral proteinase and retrotranscriptase, P5, is important for the nuclear export by TREX-1. We also demonstrated that CaMV 35S RNA leader region and especially its highly structured stem-loop is a cis-acting element recognized by the mRNAs nuclear export machinery.Chez les métazoaires et leurs virus la majorité des ARNm est exportée du noyau par les exportines TAP-p15 et le complexe TREX-1, alors qu’une minorité est exportée par CRM1. Chez les plantes ce processus fondamental reste peu décrit voir inconnu pour les phytovirus comme le CaMV et ses ARNm 19S et 35S. Notre objectif a été de clarifier cette étape primordiale mais jamais étudiée du cycle de CaMV et de l'utiliser pour mieux comprendre l'export nucléaire des ARNm chez la plante modèle Arabidopsis thaliana. Nos principaux résultats montrent que le CaMV utilise les deux voies d’export, celle de TREX-1 et celle de CRM1, pour exporter ses ARN 35S et que le précurseur de sa protéase et transcriptase inverse, P5, est important pour l’export par TREX-1. Nous avons également démontré que la région leader de ces ARN viraux, et en particulier sa structure secondaire, est un élément reconnu par la machinerie d’export nucléaire

Study of Cauliflower Mosaic Virus (CaMV) mRNAs nuclear export in Arabidopsis thaliana

Chez les métazoaires et leurs virus la majorité des ARNm est exportée du noyau par les exportines TAP-p15 et le complexe TREX-1, alors qu’une minorité est exportée par CRM1. Chez les plantes ce processus fondamental reste peu décrit voir inconnu pour les phytovirus comme le CaMV et ses ARNm 19S et 35S. Notre objectif a été de clarifier cette étape primordiale mais jamais étudiée du cycle de CaMV et de l'utiliser pour mieux comprendre l'export nucléaire des ARNm chez la plante modèle Arabidopsis thaliana. Nos principaux résultats montrent que le CaMV utilise les deux voies d’export, celle de TREX-1 et celle de CRM1, pour exporter ses ARN 35S et que le précurseur de sa protéase et transcriptase inverse, P5, est important pour l’export par TREX-1. Nous avons également démontré que la région leader de ces ARN viraux, et en particulier sa structure secondaire, est un élément reconnu par la machinerie d’export nucléaire.In metazoa most of the mature cellular and viral mRNAs are exported out of the nucleus via the TAP-p15 export receptors and their associated TREX-1 complex while a minority is exported by the exportin CRM1. In plants, this fundamental process is poorly known and even unknown for DNA phytoviruses such as CaMV and its 19S and 35S mRNAs. Our aim was to clarify this important but never studied step in CaMV life cycle in order to decode the mechanisms of mRNAs nuclear export in the model plant Arabidopsis thaliana. Our main results show that CaMV uses both the TREX-1 complex pathway as well as CRM1 to export its 35S mRNAs, and that the precursor of the viral proteinase and retrotranscriptase, P5, is important for the nuclear export by TREX-1. We also demonstrated that CaMV 35S RNA leader region and especially its highly structured stem-loop is a cis-acting element recognized by the mRNAs nuclear export machinery

Strength in Diversity: Nuclear Export of Viral RNAs

The nuclear export of cellular mRNAs is a complex process that requires the orchestrated participation of many proteins that are recruited during the early steps of mRNA synthesis and processing. This strategy allows the cell to guarantee the conformity of the messengers accessing the cytoplasm and the translation machinery. Most transcripts are exported by the exportin dimer Nuclear RNA export factor 1 (NXF1)–NTF2-related export protein 1 (NXT1) and the transcription–export complex 1 (TREX1). Some mRNAs that do not possess all the common messenger characteristics use either variants of the NXF1–NXT1 pathway or CRM1, a different exportin. Viruses whose mRNAs are synthesized in the nucleus (retroviruses, the vast majority of DNA viruses, and influenza viruses) exploit both these cellular export pathways. Viral mRNAs hijack the cellular export machinery via complex secondary structures recognized by cellular export factors and/or viral adapter proteins. This way, the viral transcripts succeed in escaping the host surveillance system and are efficiently exported for translation, allowing the infectious cycle to proceed. This review gives an overview of the cellular mRNA nuclear export mechanisms and presents detailed insights into the most important strategies that viruses use to export the different forms of their RNAs from the nucleus to the cytoplasm

Strength in Diversity: Nuclear Export of Viral RNAs.

peer reviewedThe nuclear export of cellular mRNAs is a complex process that requires the orchestrated participation of many proteins that are recruited during the early steps of mRNA synthesis and processing. This strategy allows the cell to guarantee the conformity of the messengers accessing the cytoplasm and the translation machinery. Most transcripts are exported by the exportin dimer Nuclear RNA export factor 1 (NXF1)-NTF2-related export protein 1 (NXT1) and the transcription-export complex 1 (TREX1). Some mRNAs that do not possess all the common messenger characteristics use either variants of the NXF1-NXT1 pathway or CRM1, a different exportin. Viruses whose mRNAs are synthesized in the nucleus (retroviruses, the vast majority of DNA viruses, and influenza viruses) exploit both these cellular export pathways. Viral mRNAs hijack the cellular export machinery via complex secondary structures recognized by cellular export factors and/or viral adapter proteins. This way, the viral transcripts succeed in escaping the host surveillance system and are efficiently exported for translation, allowing the infectious cycle to proceed. This review gives an overview of the cellular mRNA nuclear export mechanisms and presents detailed insights into the most important strategies that viruses use to export the different forms of their RNAs from the nucleus to the cytoplasm

Transfection of small non-coding RNAs into Arabidopsis thaliana protoplasts

International audienc

Nuclear export of plant pararetrovirus mRNAs involves the TREX complex, two viral proteins and the highly structured 5′ leader region

In eukaryotes, the major nuclear export pathway for mature mRNAs uses the dimeric receptor TAP/p15, which is recruited to mRNAs via the multisubunit TREX complex, comprising the THO core and different export adaptors. Viruses that replicate in the nucleus adopt different strategies to hijack cellular export factors and achieve cytoplasmic translation of their mRNAs. No export receptors are known in plants, but Arabidopsis TREX resembles the mammalian complex, with a conserved hexameric THO core associated with ALY and UIEF proteins, as well as UAP56 and MOS11. The latter protein is an orthologue of mammalian CIP29. The nuclear export mechanism for viral mRNAs has not been described in plants. To understand this process, we investigated the export of mRNAs of the pararetrovirus CaMV in Arabidopsis and demonstrated that it is inhibited in plants deficient in ALY, MOS11 and/or TEX1. Deficiency for these factors renders plants partially resistant to CaMV infection. Two CaMV proteins, the coat protein P4 and reverse transcriptase P5, are important for nuclear export. P4 and P5 interact and co-localise in the nucleus with the cellular export factor MOS11. The highly structured 5' leader region of 35S RNAs was identified as an export enhancing element that interacts with ALY1, ALY3 and MOS11 in vitro

Nuclear export of plant pararetrovirus mRNAs involves the TREX complex, two viral proteins and the highly structured 5' leader region.

peer reviewedIn eukaryotes, the major nuclear export pathway for mature mRNAs uses the dimeric receptor TAP/p15, which is recruited to mRNAs via the multisubunit TREX complex, comprising the THO core and different export adaptors. Viruses that replicate in the nucleus adopt different strategies to hijack cellular export factors and achieve cytoplasmic translation of their mRNAs. No export receptors are known in plants, but Arabidopsis TREX resembles the mammalian complex, with a conserved hexameric THO core associated with ALY and UIEF proteins, as well as UAP56 and MOS11. The latter protein is an orthologue of mammalian CIP29. The nuclear export mechanism for viral mRNAs has not been described in plants. To understand this process, we investigated the export of mRNAs of the pararetrovirus CaMV in Arabidopsis and demonstrated that it is inhibited in plants deficient in ALY, MOS11 and/or TEX1. Deficiency for these factors renders plants partially resistant to CaMV infection. Two CaMV proteins, the coat protein P4 and reverse transcriptase P5, are important for nuclear export. P4 and P5 interact and co-localise in the nucleus with the cellular export factor MOS11. The highly structured 5' leader region of 35S RNAs was identified as an export enhancing element that interacts with ALY1, ALY3 and MOS11 in vitro