PIN domain of Nob1p is required for D-site cleavage in 20S pre-rRNA

RNA. 2004 Nov;10(11):1698-701. doi: 10.1261/rna.7123504. Epub 2004 Sep 23.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Amino Acid Substitution
  • Base Sequence
  • Binding Sites
  • Carrier Proteins / metabolism*
  • Conserved Sequence
  • Fungal Proteins / metabolism*
  • Models, Molecular
  • Nuclear Proteins
  • Point Mutation
  • Protein Structure, Tertiary
  • RNA Precursors / metabolism*
  • RNA Processing, Post-Transcriptional
  • RNA, Ribosomal, 18S / metabolism
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae Proteins / metabolism*

Substances

  • Carrier Proteins
  • Fungal Proteins
  • NOB1 protein, S cerevisiae
  • Nuclear Proteins
  • RNA Precursors
  • RNA, Ribosomal, 18S
  • Saccharomyces cerevisiae Proteins