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Structure of the nuclear exosome captured on a maturing preribosome

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Science  08 Mar 2018:
eaar5428
DOI: 10.1126/science.aar5428

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Abstract

The RNA exosome complex processes and degrades a wide range of transcripts, including ribosomal RNAs. We used cryo-EM to visualize the yeast nuclear exosome holo-complex captured on a precursor large ribosomal subunit (pre-60S) during 7S-to-5.8S rRNA processing. The cofactors of the nuclear exosome are sandwiched between the ribonuclease core complex (Exo-10) and the remodeled “foot” structure of the pre-60S particle, which harbors the 5.8S rRNA precursor. The exosome-associated helicase Mtr4 recognizes the preribosomal substrate by docking to specific sites on the 25S rRNA, captures the 3′ extension of the 5.8S rRNA, and channels it toward Exo-10. The structure elucidates how the exosome forms a structural and functional unit together with its massive pre-60S substrate to process rRNA during ribosome maturation.

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