Abstract
Plants and invertebrates can suppress viral infection through RNA silencing, mediated by RNA-induced silencing complex (RISC). Trans-activation response RNA-binding protein (TRBP), consisting of three double-stranded RNA-binding domains, is a component of the RISC. In our previous paper, a TRBP homologue in Fenneropenaeus chinensis (Fc-TRBP) was reported to directly bind to eukaryotic initiation factor 6 (Fc-eIF6). In this study, we further characterized the function of TRBP and the involvement of TRBP and eIF6 in antiviral RNA interference (RNAi) pathway of shrimp. The double-stranded RNA binding domains (dsRBDs) B and C of the TRBP from Marsupenaeus japonicus (Mj-TRBP) were found to mediate the interaction of TRBP and eIF6. Gel-shift assays revealed that the N-terminal of Mj-TRBP dsRBD strongly binds to double-stranded RNA (dsRNA) and that the homodimer of the TRBP mediated by the C-terminal dsRBD increases the affinity to dsRNA. RNAi against either Mj-TRBP or Mj-eIF6 impairs the dsRNA-induced sequence-specific RNAi pathway and facilitates the proliferation of white spot syndrome virus (WSSV). These results further proved the important roles of TRBP and eIF6 in the antiviral response of shrimp.
Highlights
Viral diseases, especially white spot syndrome virus (WSSV) cause a great loss to the shrimp culture
In the RNA interference (RNAi) pathway, double-stranded RNA (dsRNA) was processed into Small interfering RNA (siRNA) by Dicer, and siRNA was assembled into large ribonucleoprotein complexes called RNA-induced silencing complex (RISC), the core of which is composed of Dicer, Argonaute 2 (Ago2), and transactivation response RNA-binding protein (TRBP) [2,22,23]
Since the discovery of dsRNA-mediated RNAi in C. elegans in 1998 [24], more evidence have supported the important roles of RNAi in invertebrates, plants, and fungi [25]
Summary
Especially white spot syndrome virus (WSSV) cause a great loss to the shrimp culture. Several studies demonstrate that the RNA interference (RNAi) play an important role in shrimp antiviral immunity [1]. Small interfering RNA (siRNA)/microRNA (miRNA)-induced RNA silencing has been demonstrated to be an important pathway regulating eukaryotic gene expression. This process depends on 20– 25-nt siRNAs and miRNAs, guiding the RNA-induced silencing complex (RISC) to recognize and silence the target mRNA [2,3,4]. The complex shows dicing, slicing, guide-strand selection, and Ago2-loading activities [5,6]. Introduction of those genes to Saccharomyces cerevisiae could reconstitute RNAi in budding yeast [7]. Eukaryotic initiation factor 6 (eIF6) is a component of the human RISC, depletion of eIF6 abolish the miRNA-mediated silencing [8]
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