N‐terminal Ago‐binding domain of GW182 contains a tryptophan‐rich region that confer binding to the CCR4–NOT complex

GW182 family proteins are a key component of microRNA–protein complex eliciting translational repression and/or degradation of microRNA‐targets. The microRNAs in complex with Argonaute proteins bind to target mRNAs, and GW182 proteins are recruited by association with Argonaute proteins. The GW182 protein acts as a scaffold that links the Argonaute protein to silencing machineries including the CCR4–NOT complex which accelerates deadenylation and inhibits translation. The carboxyl‐terminal effector domain of GW182 protein, also called the silencing domain, has been shown to bind to the subunits of the CCR4–NOT complex, the CNOT1 and the CNOT9. Here we show that a small region within the amino‐terminal Argonaute‐binding domain of human GW182/TNRC6A can associate with the CCR4–NOT complex. This region resides between the two Argonaute‐binding sites and contains reiterated GW/WG‐motifs. Alanine mutation experiments showed that multiple tryptophan residues are required for the association with the CCR4–NOT complex. Furthermore, co‐expression and immunoprecipitation assays suggested that the CNOT9 subunit of the CCR4–NOT complex is a possible binding partner of this region. Our work, taken together with previous studies, indicates that the human GW182 protein contains multiple binding interfaces to the CCR4–NOT complex.

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