The Putative RNA Helicase Dbp4p Is Required for Release of the U14 snoRNA from Preribosomes in Saccharomyces cerevisiae

Mol Cell. 2005 Oct 7;20(1):53-64. doi: 10.1016/j.molcel.2005.08.022.

Abstract

Around 70 yeast snoRNAs guide rRNA modification, frequently forming base-paired interactions predicted to be very stable at physiological temperatures. Eighteen putative RNA helicases are required for ribosome synthesis, but their actual substrates were not known. We report that depletion of the DEAD box helicase Dbp4p dramatically increased cosedimentation of the snoRNAs U14 and snR41 with preribosomes. Cosedimentation was maintained after deproteinization by proteinase K, indicating that the snoRNAs remained base paired to the pre-rRNA. Affinity purification showed that U14 was strongly accumulated in early 90S preribosomes and depleted from later pre-40S complexes. U14 is required for pre-rRNA processing, and depletion of Dbp4p caused a very similar pre-rRNA processing defect, perhaps due to the reduced pool of free U14. Point mutations in helicase motifs I and III of Dbp4p blocked release of U14 from preribosomes. We conclude that the helicase activity of Dbp4p is required to unwind U14 and snR41 from the pre-rRNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Motifs / physiology
  • DEAD-box RNA Helicases
  • RNA Nucleotidyltransferases / chemistry
  • RNA Nucleotidyltransferases / metabolism*
  • RNA Precursors / chemistry
  • RNA Precursors / metabolism*
  • RNA Processing, Post-Transcriptional / physiology*
  • RNA, Fungal / chemistry
  • RNA, Fungal / isolation & purification
  • RNA, Fungal / metabolism*
  • RNA, Small Nucleolar / chemistry
  • RNA, Small Nucleolar / isolation & purification
  • RNA, Small Nucleolar / metabolism*
  • Ribosomes / chemistry
  • Ribosomes / metabolism
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / chemistry
  • Saccharomyces cerevisiae Proteins / metabolism*

Substances

  • RNA Precursors
  • RNA, Fungal
  • RNA, Small Nucleolar
  • Saccharomyces cerevisiae Proteins
  • RNA Nucleotidyltransferases
  • HCA4 protein, S cerevisiae
  • DEAD-box RNA Helicases