Conserved composition of mammalian box H/ACA and box C/D small nucleolar ribonucleoprotein particles and their interaction with the common factor Nopp140

Mol Biol Cell. 2000 Feb;11(2):567-77. doi: 10.1091/mbc.11.2.567.

Abstract

Small nucleolar ribonucleoprotein particles (snoRNPs) mainly catalyze the modification of rRNA. The two major classes of snoRNPs, box H/ACA and box C/D, function in the pseudouridylation and 2'-O-methylation, respectively, of specific nucleotides. The emerging view based on studies in yeast is that each class of snoRNPs is composed of a unique set of proteins. Here we present a characterization of mammalian snoRNPs. We show that the previously characterized NAP57 is specific for box H/ACA snoRNPs, whereas the newly identified NAP65, the rat homologue of yeast Nop5/58p, is a component of the box C/D class. Using coimmunoprecipitation experiments, we show that the nucleolar and coiled-body protein Nopp140 interacts with both classes of snoRNPs. This interaction is corroborated in vivo by the exclusive depletion of snoRNP proteins from nucleoli in cells transfected with a dominant negative Nopp140 construct. Interestingly, RNA polymerase I transcription is arrested in nucleoli depleted of snoRNPs, raising the possibility of a feedback mechanism between rRNA modification and transcription. Moreover, the Nopp140-snoRNP interaction appears to be conserved in yeast, because depletion of Srp40p, the yeast Nopp140 homologue, in a conditional lethal strain induces the loss of box H/ACA small nucleolar RNAs. We propose that Nopp140 functions as a chaperone of snoRNPs in yeast and vertebrate cells.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Animals
  • COS Cells
  • Cell Nucleolus / chemistry
  • Cell Nucleolus / enzymology
  • Cell Nucleolus / metabolism
  • Conserved Sequence* / genetics
  • Epistasis, Genetic
  • Genetic Complementation Test
  • Hydro-Lyases*
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • Molecular Chaperones / genetics
  • Molecular Chaperones / metabolism
  • Molecular Sequence Data
  • Molecular Weight
  • Mutation / genetics
  • Nuclear Proteins / chemistry
  • Nuclear Proteins / deficiency
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Phosphoproteins / deficiency
  • Phosphoproteins / genetics
  • Phosphoproteins / metabolism*
  • Protein Binding
  • RNA Polymerase I / metabolism
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Rats
  • Ribonucleoproteins / chemistry
  • Ribonucleoproteins / metabolism
  • Ribonucleoproteins, Small Nuclear*
  • Ribonucleoproteins, Small Nucleolar / chemistry*
  • Ribonucleoproteins, Small Nucleolar / deficiency
  • Ribonucleoproteins, Small Nucleolar / genetics
  • Ribonucleoproteins, Small Nucleolar / metabolism*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae Proteins*
  • Serine-Arginine Splicing Factors
  • Transcription, Genetic / genetics
  • Transcription, Genetic / physiology

Substances

  • Microtubule-Associated Proteins
  • Molecular Chaperones
  • NAP57
  • NOLC1 protein, human
  • NOP58 protein, S cerevisiae
  • Nolc1 protein, rat
  • Nop58 protein, rat
  • Nuclear Proteins
  • Phosphoproteins
  • RNA-Binding Proteins
  • Ribonucleoproteins
  • Ribonucleoproteins, Small Nuclear
  • Ribonucleoproteins, Small Nucleolar
  • Saccharomyces cerevisiae Proteins
  • Serine-Arginine Splicing Factors
  • RNA Polymerase I
  • Hydro-Lyases
  • CBF5 protein, S cerevisiae