title: Ssf1p prevents premature processing of an early pre-60S ribosomal particle.
abstract: Ssf1p and Ssf2p are two nearly identical and functionally redundant nucleolar proteins. In the absence of Ssf1p and Ssf2p, the 27SA(2) pre-rRNA was prematurely cleaved, inhibiting synthesis of the 27SB and 7S pre-rRNAs and the 5.8S and 25S rRNA components of the large ribosomal subunit. On sucrose gradients, Ssf1p sedimented with pre-60S ribosomal particles. The 27SA(2), 27SA(3), and 27SB pre-rRNAs were copurified with tagged Ssf1p, as were 23 large subunit ribosomal proteins and 21 other proteins implicated in ribosome biogenesis. These included four Brix family proteins, Ssf1p, Rpf1p, Rpf2p, and Brx1p, indicating that the entire family functions in ribosome synthesis. This complex is distinct from recently reported pre-60S complexes in RNA and protein composition. We describe a multistep pathway of 60S preribosome maturation.
authors.affiliation: Wellcome Trust Centre for Cell Biology, United Kingdom.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Fatica
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Cronshaw
authors.forename: Mensur
authors.initials: M
authors.lastname: Dlakić
authors.forename: David
authors.initials: D
authors.lastname: Tollervey
mesh_terms: D000595:Amino Acid Sequence; D002499:Centrifugation, Density Gradient; D016384:Consensus Sequence; D017353:Gene Deletion; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D005810:Multigene Family; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012335:RNA, Ribosomal / Q000096:biosynthesis; D012340:RNA, Ribosomal, 5.8S / Q000096:biosynthesis; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D046911:Macromolecular Substances; D009687:Nuclear Proteins; D012322:RNA Precursors; D012335:RNA, Ribosomal; D012340:RNA, Ribosomal, 5.8S; C114037:SSF1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C065039:RNA, ribosomal, 25S