Specific recognition and ubiquitination of translating ribosomes by mammalian CCR4-NOT.

Translation affects messenger RNA stability and, in yeast, this is mediated by the Ccr4-Not deadenylation complex. The details of this process in mammals remain unclear. Here, we use cryogenic electron microscopy (cryo-EM) and crosslinking mass spectrometry to show that mammalian CCR4-NOT specifically recognizes ribosomes that are stalled during translation elongation in an in vitro reconstituted system with rabbit and human components. Similar to yeast, mammalian CCR4-NOT inserts a helical bundle of its CNOT3 subunit into the empty E site of the ribosome. Our cryo-EM structure shows that CNOT3 also locks the L1 stalk in an open conformation to inhibit further translation. CCR4-NOT is required for stable association of the nonconstitutive subunit CNOT4, which ubiquitinates the ribosome, likely to signal stalled translation elongation. Overall, our work shows that human CCR4-NOT not only detects but also enforces ribosomal stalling to couple translation and mRNA decay. © 2023. The Author(s), under exclusive licence to Springer Nature America, Inc.

Citation

Eva Absmeier, Viswanathan Chandrasekaran, Francis J O'Reilly, James A W Stowell, Juri Rappsilber, Lori A Passmore. Specific recognition and ubiquitination of translating ribosomes by mammalian CCR4-NOT. Nature structural & molecular biology. 2023 Sep;30(9):1314-1322

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PMID: 37653243

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