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  • The EMBO Journal (2003) 22, 5230 - 5240
  • doi:10.1093/emboj/cdg483

TRiC/CCT cooperates with different upstream chaperones in the folding of distinct protein classes

Katja Siegers1,2, Bettina Bölter1,2, Juliane P. Schwarz1, Ulrike M. K. Böttcher1, Suranjana Guha1 and F. Ulrich Hartl1

  1. Max Planck Institute of Biochemistry, Department of Cellular Biochemistry, D-82152 Martinsried, Germany
  2. K.Siegers and B.Bölter contributed equally to this work

Correspondence to:

Katja Siegers, E-mail: siegers@biochem.mpg.de

Received 23 June 2003; Accepted 4 August 2003; Revised 31 July 2003

The role in protein folding of the eukaryotic chaperonin TRiC/CCT is only partially understood. Here, we show that a group of WD40 beta-propeller proteins in the yeast cytosol interact transiently with TRiC upon synthesis and require the chaperonin to reach their native state. TRiC cooperates in the folding of these proteins with the ribosome-associated heat shock protein (Hsp)70 chaperones Ssb1/2p. In contrast, newly synthesized actin and tubulins, the major known client proteins of TRiC, are independent of Ssb1/2p and instead use the co-chaperone GimC/prefoldin for efficient transfer to the chaperonin. GimC can replace Ssb1/2p in the folding of WD40 substrates such as Cdc55p, but combined deletion of SSB and GIM genes results in loss of viability. These findings expand the substrate range of the eukaryotic chaperonin by a structurally defined class of proteins and demonstrate an essential role for upstream chaperones in TRiC-assisted folding.

  • Keywords:

    • chaperonin-assisted folding,
    • GimC,
    • Ssb-type Hsp70,
    • TRiC,
    • WD40 proteins