Dimerization and nuclear entry of mPER proteins in mammalian cells

  1. Kazuhiro Yagita1,
  2. Shun Yamaguchi1,
  3. Filippo Tamanini2,
  4. Gijsbertus T.J. van der Horst2,
  5. Jan H.J. Hoeijmakers2,
  6. Akira Yasui3,
  7. Jennifer J. Loros4,
  8. Jay C. Dunlap4, and
  9. Hitoshi Okamura1,5
  1. 1Department of Anatomy and Brain Science, Kobe University School of Medicine, Chuoku, Kobe 650-0017, Japan; 2MGC, Department of Cell Biology and Genetics, Erasmus University, 3000 DR, Rotterdam, The Netherlands; 3Department of Molecular Genetics, Institute of Development, Aging, and Cancer, Tohoku University, Sendai 980-8575, Japan; 4Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755 USA

Abstract

Nuclear entry of circadian oscillatory gene products is a key step for the generation of a 24-hr cycle of the biological clock. We have examined nuclear import of clock proteins of the mammalianperiod gene family and the effect of serum shock, which induces a synchronous clock in cultured cells. Previously, mCRY1 and mCRY2 have been found to complex with PER proteins leading to nuclear import. Here we report that nuclear translocation of mPER1 and mPER2 (1) involves physical interactions with mPER3, (2) is accelerated by serum treatment, and (3) still occurs in mCry1/mCry2double-deficient cells lacking a functional biological clock. Moreover, nuclear localization of endogenous mPER1 was observed in culturedmCry1/mCry2 double-deficient cells as well as in the liver and the suprachiasmatic nuclei (SCN) ofmCry1/mCry2 double-mutant mice. This indicates that nuclear translocation of at least mPER1 also can occur under physiological conditions (i.e., in the intact mouse) in the absence of any CRY protein. The mPER3 amino acid sequence predicts the presence of a cytoplasmic localization domain (CLD) and a nuclear localization signal (NLS). Deletion analysis suggests that the interplay of the CLD and NLS proposed to regulate nuclear entry of PER in Drosophilais conserved in mammals, but with the novel twist that mPER3 can act as the dimerizing partner.

Keywords

Footnotes

  • 5 Corresponding author.

  • E-MAIL okamurah{at}kobe-u.ac.jp; FAX 81 78 382 5341.

    • Received December 20, 1999.
    • Accepted April 12, 2000.
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