A functional chaperone triad on the yeast ribosome

Proc Natl Acad Sci U S A. 2002 Apr 2;99(7):4209-14. doi: 10.1073/pnas.062048599.

Abstract

The chaperones RAC (ribosome-associated complex), consisting of Ssz1p and zuotin, and Ssb1/2p are associated with ribosomes of yeast. Ssb1/2p was previously shown to form a crosslink product to polypeptides trapped in ribosome-nascent chain complexes (RNCs) in vitro. Here we show that an efficient crosslink of the nascent chain to Ssb1/2p depends on the presence of functional RAC. The crosslink to Ssb1/2p was significantly diminished if (i) RAC was removed from RNCs: a process reversed by addition of purified RAC; (ii) RAC carried a mutation in the J-domain of zuotin, leading to its inactivation in vivo; (iii) RAC's Ssz1p subunit was absent because RNCs were generated in a Deltassz1-derived translation extract. In vivo the same specific set of growth defects caused by the absence of any of the three chaperones was also displayed by a Deltassb1/2Deltassz1Deltazuo1 strain. The combination of in vitro and in vivo data supports a model in which Ssb1/2p, Ssz1p, and zuotin act in concert on nascent chains while they are being synthesized.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / physiology*
  • Fungal Proteins / chemistry
  • Fungal Proteins / physiology*
  • HSP70 Heat-Shock Proteins / chemistry
  • HSP70 Heat-Shock Proteins / physiology*
  • Molecular Chaperones / physiology*
  • Ribosomes / metabolism*
  • Saccharomyces cerevisiae / chemistry
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / physiology*
  • Saccharomyces cerevisiae Proteins*
  • Schizosaccharomyces pombe Proteins*

Substances

  • DNA-Binding Proteins
  • Fungal Proteins
  • HSP70 Heat-Shock Proteins
  • Molecular Chaperones
  • SSB1 protein, S cerevisiae
  • SSB2 protein, S pombe
  • SSZ1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Schizosaccharomyces pombe Proteins
  • ZUO1 protein, S cerevisiae