ИСТИНА

Using computer prediction and circular dichroism, we demonstrated that the nonstructural 16K protein of tobacco rattle virus (TRV, tobravirus), a suppressor of post-transcriptional gene silencing, consists of two structural parts: an ordered N-terminal region containing two putative a-structure “zinc fingers”, and a fully disordered C-terminal region with two independent bipartite nuclear localization signals (NLSs) (Ghazala et al., 2008). The protein possesses RNA-binding and oligomerization activities. We have shown that the protein has at least three RNA-binding sites, interacts with small RNAs and binds to single-stranded sRNAs more efficiently than to double-stranded (ds) sRNAs. We identified plant coilin as a major cellular partner of the viral 16K protein. Coilin acts as the structural scaffolding protein of Cajal bodies (CBs), which are dynamic subnuclear compartments. According to our results (Shaw et al., 2014) coilin/CB deficient Nicotiana benthamiana RNAi knockdown plants have intensified TRV infection, resulting in persistent severe systemic symptoms. We have demonstrated that the TRV 16K protein and plant coilin directly interact in vitro and have mapped the sites of the interaction using Far-Western assays and a set of deletion and point mutant proteins. The 16K protein is a multifunctional protein that participates in several biological activities in vivo. The in vitro properties could reflect many roles of the 16K protein in the infection cycle. This work was supported by RFBR, the grant 13-04-01467a.