PMID:16006510
| Citation |
Chellappan, P, Vanitharani, R and Fauquet, CM (2005) MicroRNA-binding viral protein interferes with Arabidopsis development. Proc. Natl. Acad. Sci. U.S.A. 102:10381-6 |
|---|---|
| Abstract |
MicroRNAs (miRNAs) are small (approximately 21 nt), noncoding RNAs that negatively regulate target mRNAs at the posttranscriptional level that are involved in development. In plants, virus-induced disease symptoms often result in developmental abnormalities resembling perturbation of miRNA-mediated function. Here, we report that expression in transgenic plants of a geminivirus-encoded AC4 protein from African cassava mosaic virus Cameroon Strain (ACMV), a suppressor of posttranscriptional gene silencing, was correlated with decreased accumulation of host miRNAs and increased development abnormalities in Arabidopsis. Down-regulation of miRNA correlated with an up-regulation of target mRNA level. In vitro binding assays revealed the ability of AC4 of ACMV (A-AC4) but not East African cassava mosaic Cameroon virus AC2 to bind single-stranded forms of miRNAs and short interfering RNAs but not double-stranded RNA forms. Normally, a labile intermediate during the miRNA biogenesis/RNA-induced silencing complex assembly, miRNA*, was below the level of detection, indicating that AC4 might interfere at a point downstream of the miRNA duplex unwinding process. The association of AC4 with miRNA was demonstrated by the association of A-AC4-GFP fusion protein, extracted from Arabidopsis protoplasts, with 2'-O-methyloligonucleotide complementary to miR159 (miR159*) and by the presence of miRNA with the A-AC4-GFP fusion protein after immunoprecipitation with antibody against GFP. In both assays, A-AC4 protein and miRNA complexes were copurified. These results provide direct evidence that AC4 is a unique virus-encoded posttranscriptional gene-silencing suppressor protein that binds to and presumably inactivates mature miRNAs and thus blocks the normal miRNA-mediated regulation of target mRNAs, resulting in developmental defects in Arabidopsis. |
| Links |
PubMed PMC1177406 Online version:10.1073/pnas.0504439102 |
| Keywords |
Arabidopsis/genetics; Arabidopsis/growth & development; Blotting, Northern; DNA Primers; Gene Silencing; Green Fluorescent Proteins; Immunoprecipitation; MicroRNAs/metabolism; Mosaic Viruses/genetics; Plant Diseases/genetics; Plant Diseases/virology; Plants, Genetically Modified; Protein Binding; Species Specificity; Viral Proteins/genetics; Viral Proteins/metabolism |
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