Suppression of Methylation-Mediated Transcriptional Gene Silencing by beta C1-SAHH Protein Interaction during Geminivirus-Betasatellite Infection

文献类型： 外文期刊

第一作者： Yang, Xiuling

作者： Yang, Xiuling;Xie, Yan;Shen, Qingtang;Zhou, Xueping;Raja, Priya;Li, Sizhun;Wolf, Jamie N.;Bisaro, David M.;Raja, Priya;Li, Sizhun;Wolf, Jamie N.;Bisaro, David M.

作者机构：

期刊名称：PLOS PATHOGENS （ 影响因子：6.823； 五年影响因子：7.455 ）

ISSN： 1553-7366

年卷期： 2011 年 7 卷 10 期

页码：

收录情况： SCI

摘要： DNA methylation is a fundamental epigenetic modification that regulates gene expression and represses endogenous transposons and invading DNA viruses. As a counter-defense, the geminiviruses encode proteins that inhibit methylation and transcriptional gene silencing (TGS). Some geminiviruses have acquired a betasatellite called DNA beta. This study presents evidence that suppression of methylation-mediated TGS by the sole betasatellite-encoded protein, beta C1, is crucial to the association of Tomato yellow leaf curl China virus (TYLCCNV) with its betasatellite (TYLCCNB). We show that TYLCCNB complements Beet curly top virus (BCTV) L2(-) mutants deficient for methylation inhibition and TGS suppression, and that cytosine methylation levels in BCTV and TYLCCNV genomes, as well as the host genome, are substantially reduced by TYLCCNB or beta C1 expression. We also demonstrate that while TYLCCNB or beta C1 expression can reverse TGS, TYLCCNV by itself is ineffective. Thus its AC2/AL2 protein, known to have suppression activity in other geminiviruses, is likely a natural mutant in this respect. A yeast two-hybrid screen of candidate proteins, followed by bimolecular fluorescence complementation analysis, revealed that beta C1 interacts with S-adenosyl homocysteine hydrolase (SAHH), a methyl cycle enzyme required for TGS. We further demonstrate that beta C1 protein inhibits SAHH activity in vitro. That beta C1 and other geminivirus proteins target the methyl cycle suggests that limiting its product, S-adenosyl methionine, may be a common viral strategy for methylation interference. We propose that inhibition of methylation and TGS by beta C1 stabilizes geminivirus/betasatellite complexes.

分类号： Microbiology; Parasitology; Virology

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