Vargason Jeffrey M, Szittya György, Burgyán József, Hall Traci M Tanka
Laboratory of Structural Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
Cell. 2003 Dec 26;115(7):799-811. doi: 10.1016/s0092-8674(03)00984-x.
RNA silencing in plants likely exists as a defense mechanism against molecular parasites such as RNA viruses, retrotransposons, and transgenes. As a result, many plant viruses have adapted mechanisms to evade and suppress gene silencing. Tombusviruses express a 19 kDa protein (p19), which has been shown to suppress RNA silencing in vivo and bind silencing-generated and synthetic small interfering RNAs (siRNAs) in vitro. Here we report the 2.5 A crystal structure of p19 from the Carnation Italian ringspot virus (CIRV) bound to a 21 nt siRNA and demonstrate in biochemical and in vivo assays that CIRV p19 protein acts as a molecular caliper to specifically select siRNAs based on the length of the duplex region of the RNA.
植物中的RNA沉默可能作为一种防御机制，抵御诸如RNA病毒、逆转录转座子和转基因等分子寄生物。因此，许多植物病毒已进化出逃避和抑制基因沉默的机制。番茄丛矮病毒表达一种19 kDa的蛋白（p19），该蛋白已被证明在体内可抑制RNA沉默，并在体外结合由沉默产生的和合成的小干扰RNA（siRNA）。在此，我们报道了来自康乃馨意大利环斑病毒（CIRV）的p19与一个21 nt siRNA结合的2.5 Å晶体结构，并在生化和体内实验中证明，CIRV p19蛋白作为一个分子卡尺，根据RNA双链区的长度特异性选择siRNA。
