RNA silencing is a conserved eukaryotic pathway involved in the suppression of gene expression via sequence-specific interactions that are mediated by 21–23 nt RNA molecules.During infection,RNAi can act as an innate...RNA silencing is a conserved eukaryotic pathway involved in the suppression of gene expression via sequence-specific interactions that are mediated by 21–23 nt RNA molecules.During infection,RNAi can act as an innate immune system to defend against viruses.As a counter-defensive strategy,silencing suppressors are encoded by viruses to inhibit various stages of the silencing process.These suppressors are diverse in sequence and structure and act via different mechanisms.In this review,we discuss whether RNAi is a defensive strategy in mammalian host cells and whether silencing suppressors can be encoded by mammalian viruses.We also review the modes of action proposed for some silencing suppressors.展开更多
RNA silencing is a conserved mechanism found ubiquitously in eukaryotic organisms.It has been used to regulate gene expression and development.In addition,RNA silencing serves as an important mechanism in plants' ...RNA silencing is a conserved mechanism found ubiquitously in eukaryotic organisms.It has been used to regulate gene expression and development.In addition,RNA silencing serves as an important mechanism in plants' defense against invasive nucleic acids,such as viruses,transposons,and transgenes.As a counter-defense,most plants,and some animal viruses,encode RNA silencing suppressors to interfere at one or several points of the silencing pathway.In this study,we showed that Pns12 of RGDV (Rice gall dwarf virus) exhibits silencing suppressor activity on the reporter green fluorescent protein in transgenic Nicotiana benthamiana line 16c.Pns12 of RGDV suppressed local silencing induced by sense RNA but had no effect on that induced by dsRNA.Expression of Pns12 also enhanced Potato virus X pathogenicity in N.benthamiana.Collectively,these results suggested that RGDV Pns12 functions as a virus suppressor of RNA silencing,which might target an upstream step of dsRNA formation in the RNA silencing pathway.Furthermore,we showed that Pns12 is localized mainly in the nucleus of N.benthamiana leaf cells.展开更多
Gene silencing (RNA silencing) plays a fundamental role in antiviral defense in plants, fungi and invertebrates. Viruses encode proteins that suppress gene silencing to counter host defense. Viral suppressors of RNA s...Gene silencing (RNA silencing) plays a fundamental role in antiviral defense in plants, fungi and invertebrates. Viruses encode proteins that suppress gene silencing to counter host defense. Viral suppressors of RNA silencing (VSRs) have been identified from almost all plant virus genera and some viruses of insects and mammals. Recent studies have revealed that VSRs counter host defense and interfere with host gene regulation by interacting with RNA or important components of the RNA silencing pathway. Here, we review the current understanding of the complex mechanisms of VSRs that have been revealed by recent studies.展开更多
RNA silencing is a potent antiviral mechanism in plants and animals. As a counter-defense, many viruses studied to date encode one or more viral suppressors of RNA silencing(VSR). In the latter case, how different VSR...RNA silencing is a potent antiviral mechanism in plants and animals. As a counter-defense, many viruses studied to date encode one or more viral suppressors of RNA silencing(VSR). In the latter case, how different VSRs encoded by a virus function in silencing remains to be fully understood. We previously showed that the nonstructural protein Pns10 of a Phytoreovirus, Rice dwarf virus(RDV), functions as a VSR. Here we present evidence that another nonstructural protein, Pns11, also functions as a VSR. While Pns10 was localized in the cytoplasm, Pns11 was localized both in the nucleus and chloroplasts. Pns11 has two bipartite nuclear localization signals(NLSs), which were required for nuclear as well as chloroplastic localization. The NLSs were also required for the silencing activities of Pns11. This is the first report that multiple VSRs encoded by a virus are localized in different subcellular compartments, and that a viral protein can be targeted to both the nucleus and chloroplast. These findings may have broad significance in studying the subcellular targeting of VSRs and other viral proteins in viral-host interactions.展开更多
基金the National Basic Research Program(973 Project)(Grant No.2011CB504805)the National Natural Science Foundation of China(Grant No.30900759/C0709)the Postdoctoral Foundation of China.
文摘RNA silencing is a conserved eukaryotic pathway involved in the suppression of gene expression via sequence-specific interactions that are mediated by 21–23 nt RNA molecules.During infection,RNAi can act as an innate immune system to defend against viruses.As a counter-defensive strategy,silencing suppressors are encoded by viruses to inhibit various stages of the silencing process.These suppressors are diverse in sequence and structure and act via different mechanisms.In this review,we discuss whether RNAi is a defensive strategy in mammalian host cells and whether silencing suppressors can be encoded by mammalian viruses.We also review the modes of action proposed for some silencing suppressors.
基金supported by the National Basic Research Program of China(Grant No. 2010CB126203)the National Transgenic Major Program(Grant Nos. 2009ZX08009-044B and 2009ZX08001-018B)+2 种基金the National Natural Science Foundation of China(Grant No. 30970135)the Fujian Province Education Department(Grant No. JB08078)Specialized Research Fund for the Ministry of Agriculture(Grant No. nyhyzx07-051)
文摘RNA silencing is a conserved mechanism found ubiquitously in eukaryotic organisms.It has been used to regulate gene expression and development.In addition,RNA silencing serves as an important mechanism in plants' defense against invasive nucleic acids,such as viruses,transposons,and transgenes.As a counter-defense,most plants,and some animal viruses,encode RNA silencing suppressors to interfere at one or several points of the silencing pathway.In this study,we showed that Pns12 of RGDV (Rice gall dwarf virus) exhibits silencing suppressor activity on the reporter green fluorescent protein in transgenic Nicotiana benthamiana line 16c.Pns12 of RGDV suppressed local silencing induced by sense RNA but had no effect on that induced by dsRNA.Expression of Pns12 also enhanced Potato virus X pathogenicity in N.benthamiana.Collectively,these results suggested that RGDV Pns12 functions as a virus suppressor of RNA silencing,which might target an upstream step of dsRNA formation in the RNA silencing pathway.Furthermore,we showed that Pns12 is localized mainly in the nucleus of N.benthamiana leaf cells.
基金supported by the National Basic Research Program of China (Grant No. 2012CB114004)the National Natural Science Foundation of China (Grant Nos. 31030005 and 30910103904)
文摘Gene silencing (RNA silencing) plays a fundamental role in antiviral defense in plants, fungi and invertebrates. Viruses encode proteins that suppress gene silencing to counter host defense. Viral suppressors of RNA silencing (VSRs) have been identified from almost all plant virus genera and some viruses of insects and mammals. Recent studies have revealed that VSRs counter host defense and interfere with host gene regulation by interacting with RNA or important components of the RNA silencing pathway. Here, we review the current understanding of the complex mechanisms of VSRs that have been revealed by recent studies.
基金supported by grants from CARS-01-06 to X.H.X., Transgenic Research Program (2016ZX08010001)the National Natural Science Foundation of China (31530062)。
文摘RNA silencing is a potent antiviral mechanism in plants and animals. As a counter-defense, many viruses studied to date encode one or more viral suppressors of RNA silencing(VSR). In the latter case, how different VSRs encoded by a virus function in silencing remains to be fully understood. We previously showed that the nonstructural protein Pns10 of a Phytoreovirus, Rice dwarf virus(RDV), functions as a VSR. Here we present evidence that another nonstructural protein, Pns11, also functions as a VSR. While Pns10 was localized in the cytoplasm, Pns11 was localized both in the nucleus and chloroplasts. Pns11 has two bipartite nuclear localization signals(NLSs), which were required for nuclear as well as chloroplastic localization. The NLSs were also required for the silencing activities of Pns11. This is the first report that multiple VSRs encoded by a virus are localized in different subcellular compartments, and that a viral protein can be targeted to both the nucleus and chloroplast. These findings may have broad significance in studying the subcellular targeting of VSRs and other viral proteins in viral-host interactions.