Small interfering RNA (siRNA) and microRNA (miRNA) are small RNAs of 18-25 nucleotides (nt) in length that play important roles in regulating gene expression. They are incorporated into an RNA-induced silencing comple...Small interfering RNA (siRNA) and microRNA (miRNA) are small RNAs of 18-25 nucleotides (nt) in length that play important roles in regulating gene expression. They are incorporated into an RNA-induced silencing complex (RISC) and serve as guides for silencing their corresponding target mRNAs based on complementary base-pairing. The promise of gene silencing has led many researchers to consider siRNA as an anti-viral tool. However, in long-term settings, many viruses appear to escape from this therapeutical strategy. An example of this may be seen in the case of human immunodeficiency virus type-1 (HIV-1) which is able to evade RNA silencing by either mutating the siRNA- targeted sequence or by encoding for a partial suppressor of RNAi (RNA interference). On the other hand, because miRNA targeting does not require absolute complementarity of base-pairing, mutational escape by viruses from miRNA- specified silencing may be more difficult to achieve. In this review, we discuss stratagems used by various viruses to avoid the cells’ antiviral si/mi-RNA defenses and notions of how viruses might control and regulate host cell genes by encoding viral miRNAs (vmiRNAs).展开更多
RNAi is an efficient surveillance machinery that plays a robust defensive role in shielding plant and animal hosts against viral infections. In counter-defense viruses encode suppressor proteins that have the ability ...RNAi is an efficient surveillance machinery that plays a robust defensive role in shielding plant and animal hosts against viral infections. In counter-defense viruses encode suppressor proteins that have the ability to restrict the RNAi machinery to ensure successful systemic invasion. The B2 protein of insect Flock House Virus (FHV-B2) and AC2 protein of Mungbean Yellow Mosaic India Virus (MYMIV-AC2) are two well-characterized suppressors of RNAi, capable of reversing reporter gene silencing. In this study, we compared the strength of the two suppressors by assaying for the degree of RNAi reversion and the duration of sustaining the reversal in planta. The suppression activity was observed by assaying for GFP fluorescence at 3 dpi, 7 dpi and 14 dpi. The phenotypic observations were corroborated with small RNA Northern Blotting and semi-quantitative RT-PCR. The results indicate that suppressor strength of FHVB2 is comparable to MYMIV-AC2, although they are encoded by virus infecting host from two different eukaryotic kingdoms. This study will provide new insights to dissect the conservation in the RNAi pathways during the host-virus interactions.展开更多
Rice gall dwarf virus(RGDV)is an important rice pathogen in China and Southeast Asia.However,little is known about the molecular mechanisms of RGDV interactions with plant cells.Here,we have identi-fied an RGDV protei...Rice gall dwarf virus(RGDV)is an important rice pathogen in China and Southeast Asia.However,little is known about the molecular mechanisms of RGDV interactions with plant cells.Here,we have identi-fied an RGDV protein,Pns11,which acts as a suppressor of RNA silencing in coinfiltration assays with the reporter,green fluorescent protein(GFP)in transgenic Nicotiana benthamiana line 16c carrying GFP.Pns11 suppressed local and systemic silencing induced by sense RNA.The spread of mobile RNA si-lencing signals was blocked or inactivated by Pns11.Expression of Pns11 also enhanced Potato virus X pathogenicity in N.benthamiana.This suppressor could reduce,but not eliminate,siRNA in the local and systemic RNA silencing suppression assays,suggesting that Pns11 functions by interfering with initial stages of RNA silencing.展开更多
文摘Small interfering RNA (siRNA) and microRNA (miRNA) are small RNAs of 18-25 nucleotides (nt) in length that play important roles in regulating gene expression. They are incorporated into an RNA-induced silencing complex (RISC) and serve as guides for silencing their corresponding target mRNAs based on complementary base-pairing. The promise of gene silencing has led many researchers to consider siRNA as an anti-viral tool. However, in long-term settings, many viruses appear to escape from this therapeutical strategy. An example of this may be seen in the case of human immunodeficiency virus type-1 (HIV-1) which is able to evade RNA silencing by either mutating the siRNA- targeted sequence or by encoding for a partial suppressor of RNAi (RNA interference). On the other hand, because miRNA targeting does not require absolute complementarity of base-pairing, mutational escape by viruses from miRNA- specified silencing may be more difficult to achieve. In this review, we discuss stratagems used by various viruses to avoid the cells’ antiviral si/mi-RNA defenses and notions of how viruses might control and regulate host cell genes by encoding viral miRNAs (vmiRNAs).
文摘RNAi is an efficient surveillance machinery that plays a robust defensive role in shielding plant and animal hosts against viral infections. In counter-defense viruses encode suppressor proteins that have the ability to restrict the RNAi machinery to ensure successful systemic invasion. The B2 protein of insect Flock House Virus (FHV-B2) and AC2 protein of Mungbean Yellow Mosaic India Virus (MYMIV-AC2) are two well-characterized suppressors of RNAi, capable of reversing reporter gene silencing. In this study, we compared the strength of the two suppressors by assaying for the degree of RNAi reversion and the duration of sustaining the reversal in planta. The suppression activity was observed by assaying for GFP fluorescence at 3 dpi, 7 dpi and 14 dpi. The phenotypic observations were corroborated with small RNA Northern Blotting and semi-quantitative RT-PCR. The results indicate that suppressor strength of FHVB2 is comparable to MYMIV-AC2, although they are encoded by virus infecting host from two different eukaryotic kingdoms. This study will provide new insights to dissect the conservation in the RNAi pathways during the host-virus interactions.
基金the National Natural Science Foundation of China(Grant Nos.30370929 and 30671358)
文摘Rice gall dwarf virus(RGDV)is an important rice pathogen in China and Southeast Asia.However,little is known about the molecular mechanisms of RGDV interactions with plant cells.Here,we have identi-fied an RGDV protein,Pns11,which acts as a suppressor of RNA silencing in coinfiltration assays with the reporter,green fluorescent protein(GFP)in transgenic Nicotiana benthamiana line 16c carrying GFP.Pns11 suppressed local and systemic silencing induced by sense RNA.The spread of mobile RNA si-lencing signals was blocked or inactivated by Pns11.Expression of Pns11 also enhanced Potato virus X pathogenicity in N.benthamiana.This suppressor could reduce,but not eliminate,siRNA in the local and systemic RNA silencing suppression assays,suggesting that Pns11 functions by interfering with initial stages of RNA silencing.
