Protein phosphatase 1 regulates the stability of the circadian protein PER2.


Journal Article

The circadian clock is regulated by a transcription/translation negative feedback loop. A key negative regulator of circadian rhythm in mammals is the PER2 (mammalian PERIOD 2) protein. Its daily degradation at the end of the night accompanies de-repression of transcription. CKI (casein kinase I ) has been identified as the kinase that phosphorylates PER2, targeting it for ubiquitin-mediated proteasomal degradation. We now report that PER2 degradation is also negatively regulated by PP1 (protein phosphatase 1)-mediated dephosphorylation. In Xenopus egg extract, PP1 inhibition by Inhibitor-2 accelerated mPER2 degradation. Co-immunoprecipitation experiments showed that PER2 bound to PP1c in transfected HEK-293 cells. PP1 immunoprecipitated from HEK-293 cells, mouse liver and mouse brain, dephosphorylated CKI-phosphorylated PER2, showing that PER2 is a substrate for mammalian endogenous PP1. Moreover, over-expression of the dominant negative form of PP1c, the D95N mutant, accelerated ubiquitin and proteasome-mediated degradation of PER2, and shortened the PER2 half-life in HEK-293 cells. Over-expression of the PP1 inhibitors, protein phosphatase 1 holoenzyme inhibitor-1 and Inhibitor-2, confirmed these results. Thus PP1 regulates PER2 stability and is therefore a candidate to regulate mammalian circadian rhythms.

Full Text

Duke Authors

Cited Authors

  • Gallego, M; Kang, H; Virshup, DM

Published Date

  • October 1, 2006

Published In

Volume / Issue

  • 399 / 1

Start / End Page

  • 169 - 175

PubMed ID

  • 16813562

Pubmed Central ID

  • 16813562

Electronic International Standard Serial Number (EISSN)

  • 1470-8728

Digital Object Identifier (DOI)

  • 10.1042/BJ20060678


  • eng

Conference Location

  • England