90S pre-ribosome transformation into the primordial 40S subunit.
Production of small ribosomal subunits initially requires the formation of a 90S precursor followed by an enigmatic process of restructuring into the primordial pre-40S subunit. We elucidate this process by biochemical and cryo-electron microscopy analysis of intermediates along this pathway in yeast. First, the remodeling RNA helicase Dhr1 engages the ... 90S pre-ribosome, followed by Utp24 endonuclease-driven RNA cleavage at site A1, thereby separating the 5'-external transcribed spacer (ETS) from 18S ribosomal RNA. Next, the 5'-ETS and 90S assembly factors become dislodged, but this occurs sequentially, not en bloc. Eventually, the primordial pre-40S emerges, still retaining some 90S factors including Dhr1, now ready to unwind the final small nucleolar U3-18S RNA hybrid. Our data shed light on the elusive 90S to pre-40S transition and clarify the principles of assembly and remodeling of large ribonucleoproteins.
Mesh Terms:
Cryoelectron Microscopy, DEAD-box RNA Helicases, Nuclear Proteins, Protein Conformation, RNA Cleavage, RNA, Ribosomal, 18S, Ribosomal Proteins, Ribosome Subunits, Large, Eukaryotic, Ribosome Subunits, Small, Eukaryotic, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Cryoelectron Microscopy, DEAD-box RNA Helicases, Nuclear Proteins, Protein Conformation, RNA Cleavage, RNA, Ribosomal, 18S, Ribosomal Proteins, Ribosome Subunits, Large, Eukaryotic, Ribosome Subunits, Small, Eukaryotic, Saccharomyces cerevisiae, Saccharomyces cerevisiae Proteins
Science
Date: Dec. 18, 2019
PubMed ID: 32943521
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