病毒编码的转录后基因沉默抑制因子作用于沉默途径中的一个维持步骤。
Virus-encoded suppressor of posttranscriptional gene silencing targets a maintenance step in the silencing pathway.
作者信息
Llave C, Kasschau K D, Carrington J C
机构信息
Institute of Biological Chemistry, Washington State University, Pullman, WA 99164-6340, USA.
出版信息
Proc Natl Acad Sci U S A. 2000 Nov 21;97(24):13401-6. doi: 10.1073/pnas.230334397.
Certain plant viruses encode suppressors of posttranscriptional gene silencing (PTGS), an adaptive antiviral defense response that limits virus replication and spread. The tobacco etch potyvirus protein, helper component-proteinase (HC-Pro), suppresses PTGS of silenced transgenes. The effect of HC-Pro on different steps of the silencing pathway was analyzed by using both transient Agrobacterium tumefaciens-based delivery and transgenic systems. HC-Pro inactivated PTGS in plants containing a preexisting silenced beta-glucuronidase (GUS) transgene. PTGS in this system was associated with both small RNA molecules (21-26 nt) corresponding to the 3' proximal region of the transcribed GUS sequence and cytosine methylation of specific sites near the 3' end of the GUS transgene. Introduction of HC-Pro into these plants resulted in loss of PTGS, loss of small RNAs, and partial loss of methylation. These results suggest that HC-Pro targets a PTGS maintenance (as opposed to an initiation or signaling) component at a point that affects accumulation of small RNAs and methylation of genomic DNA.
某些植物病毒编码转录后基因沉默（PTGS）的抑制因子，PTGS是一种适应性抗病毒防御反应，可限制病毒的复制和传播。烟草蚀纹马铃薯Y病毒蛋白辅助成分蛋白酶（HC-Pro）可抑制沉默转基因的PTGS。通过基于根癌农杆菌的瞬时递送和转基因系统，分析了HC-Pro对沉默途径不同步骤的影响。HC-Pro使含有预先沉默的β-葡萄糖醛酸酶（GUS）转基因的植物中的PTGS失活。该系统中的PTGS与对应于转录的GUS序列3'近端区域的小RNA分子（21-26 nt）以及GUS转基因3'末端附近特定位点的胞嘧啶甲基化有关。将HC-Pro导入这些植物会导致PTGS丧失、小RNA丢失以及甲基化部分丧失。这些结果表明，HC-Pro在影响小RNA积累和基因组DNA甲基化的位点靶向PTGS维持（而非起始或信号传导）成分。
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