Molecular basis of cyclin-CDK-CKI regulation by reversible binding of an inositol pyrophosphate

Nat Chem Biol. 2008 Jan;4(1):25-32. doi: 10.1038/nchembio.2007.52. Epub 2007 Nov 25.


When Saccharomyces cerevisiae cells are starved of inorganic phosphate, the Pho80-Pho85 cyclin-cyclin-dependent kinase (CDK) is inactivated by the Pho81 CDK inhibitor (CKI). The regulation of Pho80-Pho85 is distinct from previously characterized mechanisms of CDK regulation: the Pho81 CKI is constitutively associated with Pho80-Pho85, and a small-molecule ligand, inositol heptakisphosphate (IP7), is required for kinase inactivation. We investigated the molecular basis of the IP7- and Pho81-dependent Pho80-Pho85 inactivation using electrophoretic mobility shift assays, enzyme kinetics and fluorescence spectroscopy. We found that IP7 interacts noncovalently with Pho80-Pho85-Pho81 and induces additional interactions between Pho81 and Pho80-Pho85 that prevent substrates from accessing the kinase active site. Using synthetic peptides corresponding to Pho81, we define regions of Pho81 responsible for constitutive Pho80-Pho85 binding and IP7-regulated interaction and inhibition. These findings expand our understanding of the mechanisms of cyclin-CDK regulation and of the biochemical mechanisms of IP7 action.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cyclin-Dependent Kinases / antagonists & inhibitors*
  • Cyclins / antagonists & inhibitors*
  • DNA-Binding Proteins / antagonists & inhibitors
  • Electrophoretic Mobility Shift Assay
  • Inositol Phosphates* / metabolism
  • Inositol Phosphates* / pharmacology
  • Inositol Phosphates* / physiology
  • Protein Binding
  • Recombinant Proteins / metabolism
  • Recombinant Proteins / pharmacology
  • Repressor Proteins / antagonists & inhibitors*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / metabolism*
  • Saccharomyces cerevisiae Proteins / antagonists & inhibitors*
  • Substrate Specificity
  • Transcription Factors / antagonists & inhibitors


  • Cyclins
  • DNA-Binding Proteins
  • Inositol Phosphates
  • PHO4 protein, S cerevisiae
  • PHO80 protein, S cerevisiae
  • PHO81 protein, S cerevisiae
  • Recombinant Proteins
  • Repressor Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • inositol heptakisphosphate
  • Cyclin-Dependent Kinases
  • PHO85 protein, S cerevisiae

Associated data

  • PubChem-Substance/26740886
  • PubChem-Substance/26740887
  • PubChem-Substance/26740888
  • PubChem-Substance/26740889
  • PubChem-Substance/26740890
  • PubChem-Substance/26740891