Human casein kinase Idelta phosphorylation of human circadian clock proteins period 1 and 2

FEBS Lett. 2001 Feb 2;489(2-3):159-65. doi: 10.1016/s0014-5793(00)02434-0.


Casein kinase Iepsilon (CKIepsilon), a central component of the circadian clock, interacts with and phosphorylates human period protein 1 (hPER1) [Keesler, G.A. et al. (2000) NeuroReport 5, 951-955]. A mutation in CKIepsilon causes a shortened circadian period in Syrian Golden hamster. We have now extended our previous studies to show that human casein kinase Idelta (hCKIdelta), the closest homologue to hCKIepsilon, associates with and phosphorylates hPER1 and causes protein instability. Furthermore, we observed that both hCKIdelta and hCKIepsilon phosphorylated and caused protein instability of human period 2 protein (hPER2). Immunohistochemical staining of rat brains demonstrates that CKIdelta protein is localized in the suprachiasmatic nuclei, the central location of the master clock. These results indicate that CKIdelta may play a role similar to CKIepsilon, suggesting that it may also be involved in regulating circadian rhythmicity by post-translation modification of mammalian clock proteins hPER1 and 2.

MeSH terms

  • Animals
  • Casein Kinases
  • Cell Cycle Proteins
  • Cell Line
  • DNA, Recombinant
  • Green Fluorescent Proteins
  • Humans
  • Immunohistochemistry
  • Luminescent Proteins / genetics
  • Luminescent Proteins / metabolism
  • Male
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Period Circadian Proteins
  • Phosphorylation
  • Protein Binding
  • Protein Kinases / genetics
  • Protein Kinases / metabolism*
  • Rats
  • Rats, Sprague-Dawley
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Suprachiasmatic Nucleus / enzymology
  • Transcription Factors
  • Transfection


  • Cell Cycle Proteins
  • DNA, Recombinant
  • Luminescent Proteins
  • Nuclear Proteins
  • PER1 protein, human
  • PER2 protein, human
  • Per1 protein, mouse
  • Per1 protein, rat
  • Per2 protein, mouse
  • Per2 protein, rat
  • Period Circadian Proteins
  • Recombinant Fusion Proteins
  • Transcription Factors
  • Green Fluorescent Proteins
  • Protein Kinases
  • Casein Kinases