Functioning of the Hsp90 machine in chaperoning checkpoint kinase I (Chk1) and the progesterone receptor (PR)

Cell Stress Chaperones. Winter 2007;12(4):353-63. doi: 10.1379/csc-299.1.


Hsp90 is an abundant and highly conserved chaperone that functions at later stages of protein folding to maintain and regulate the activity of client proteins. Using a recently described in vitro system to fold a functional model kinase Chk1, we performed a side-by-side comparison of the Hsp90-dependent chaperoning of Chk1 to that of the progesterone receptor (PR) and show that these distinct types of clients have different chaperoning requirements. The less stable PR required more total chaperone protein(s) and p23, whereas Chk1 folding was critically dependent on Cdc37. When the 2 clients were reconstituted under identical conditions, each client folding was dose dependent for Hsp90 protein levels and was inhibited by geldanamycin. Using this tractable system, we found that Chk1 kinase folding was more effective if we used a type II Hsp40 cochaperone, whereas PR is chaperoned equally well with a type I or type II Hsp40. Additional dissection of Chk1-chaperone complexes and the resulting kinase activity suggests that kinase folding, like that previously shown for PR, is a dynamic, multistep process. Importantly, the cochaperones Hop and Cdc37 cooperate as the kinase transitions from immature Hsp70- to mature Hsp90-predominant complexes.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Benzoquinones / pharmacology
  • Cell Cycle Proteins / metabolism
  • Chaperonins / metabolism
  • Checkpoint Kinase 1
  • Chickens
  • HSP40 Heat-Shock Proteins / metabolism
  • HSP70 Heat-Shock Proteins / metabolism
  • HSP90 Heat-Shock Proteins / chemistry
  • HSP90 Heat-Shock Proteins / metabolism*
  • Homeodomain Proteins / metabolism
  • Humans
  • Lactams, Macrocyclic / pharmacology
  • Models, Biological
  • Protein Binding / drug effects
  • Protein Folding
  • Protein Kinases / metabolism*
  • Protein Transport / drug effects
  • Receptors, Progesterone / metabolism*
  • Tumor Suppressor Proteins / metabolism


  • Benzoquinones
  • CDC37 protein, human
  • Cell Cycle Proteins
  • HOP protein, human
  • HSP40 Heat-Shock Proteins
  • HSP70 Heat-Shock Proteins
  • HSP90 Heat-Shock Proteins
  • Homeodomain Proteins
  • Lactams, Macrocyclic
  • Receptors, Progesterone
  • Tumor Suppressor Proteins
  • Protein Kinases
  • CHEK1 protein, human
  • Checkpoint Kinase 1
  • Chaperonins
  • geldanamycin