title: PIN domain of Nob1p is required for D-site cleavage in 20S pre-rRNA.
abstract: Nob1p (Yor056c) is essential for processing of the 20S pre-rRNA to the mature 18S rRNA. It is part of a pre-40S ribosomal particle that is transported to the cytoplasm and subsequently cleaved at the 3' end of mature 18S rRNA (D-site). Nob1p is also reported to participate in proteasome biogenesis, and it was therefore unclear whether its primary activity is in ribosome synthesis. In this work, we describe a homology model of the PIN domain of Nob1p, which structurally mimics Mg(2+)-dependent exonucleases despite negligible similarity in primary sequence. Insights gained from this model were used to design a point mutation that was predicted to abolish the postulated enzymatic activity. Cells expressing Nob1p with this mutation failed to cleave the 20S pre-rRNA. This supports both the significance of the structural model and the idea that Nob1p is the long-sought D-site endonuclease.
authors.affiliation: Department of Genetics and Molecular Biology, University of Rome "La Sapienza", Rome, Italy.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Fatica
authors.forename: David
authors.initials: D
authors.lastname: Tollervey
authors.forename: Mensur
authors.initials: M
authors.lastname: Dlakić
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001483:Base Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000378:metabolism*; D017124:Conserved Sequence; D005656:Fungal Proteins / Q000378:metabolism*; D008958:Models, Molecular; D009687:Nuclear Proteins; D017354:Point Mutation; D017434:Protein Structure, Tertiary; D012322:RNA Precursors / Q000378:metabolism*; D012323:RNA Processing, Post-Transcriptional; D012337:RNA, Ribosomal, 18S / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D005656:Fungal Proteins; C405962:NOB1 protein, S cerevisiae; D009687:Nuclear Proteins; D012322:RNA Precursors; D012337:RNA, Ribosomal, 18S; D029701:Saccharomyces cerevisiae Proteins