Expression of TNRC6 (GW182) Proteins Is Not Necessary for Gene Silencing by Fully Complementary RNA Duplexes

The trinucleotide repeat containing 6 (TNRC6) family of proteins are core components of RNA interference (RNAi) and consist of three paralogs (TNRC6A, TNRC6B, and TNRC6C). The TNRC6 paralogs associate with argonaute (AGO) protein, the core RNAi factor, and bridge its interactions with other proteins. We obtained TNRC6A and TNRC6B single and double knockout cell lines to investigate how the TNRC6 paralogs contribute to RNAi. We found that TNRC6 proteins are not required for gene silencing when duplex RNAs are fully complementary. TNRC6 expression was necessary for regulation by a microRNA. TNRC6A, but not TNRC6B, expression was necessary for transcriptional activation by a duplex RNA targeting a gene promoter. By contrast, AGO2 is required for all three gene expression pathways. TNRC6A can affect the Dicer localization in cytoplasm versus the nucleus, but none of the three TNRC6 paralogs was necessary for nuclear localization of AGO2. Our data suggest that the roles of the TNRC6 paralogs differ in some details and that TNRC6 is not required for clinical therapeutic silencing mechanisms that involve fully complementary duplex RNAs.