Identification of acetylation-regulated interactors of the human CCR4-NOT complex

The evolutionarily conserved CCR4-NOT complex acts as a central player in the control of mRNA turnover and mediates accelerated mRNA degradation upon histone deacetylase (HDAC) inhibition. Here, we explored acetylation-induced changes in the composition of the CCR4-NOT complex by purification of the endogenously tagged scaffold subunit NOT1 and identified ring finger protein 219 (RNF219) as an acetylation-regulated cofactor. We provide evidence that RNF219 is an active RING-type E3 ubiquitin ligase which stably associates with the CCR4-NOT complex via the NOT9 module through a short linear motif located in the C-terminal low-complexity region of RNF219. Using a reconstituted six-subunit human CCR4-NOT complex, we demonstrate that RNF219 acts as an inhibitor of deadenylation. Accordingly, our transcriptome-wide mRNA half-life measurements reveal that RNF219 attenuates global mRNA turnover in cells, independently of its E3 ligase activity. Our results establish RNF219 as a negative regulator of CCR4-NOT-mediated mRNA deadenylation, whose loss upon HDAC inhibition contributes to accelerated mRNA turnover.