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Interactive Organization of the Circadian Core Regulators PER2, BMAL1, CLOCK and PML

Takao Miki1, Zhaoyang Zhao1, Cheng Chi Lee1

  • 1Department of Biochemistry and Molecular Biology, Medical School, University of Texas Health Science Center-Houston, Houston, Texas 77030, USA.

Scientific Reports
|July 8, 2016
PubMed

Insights

PML protein is crucial for circadian clock function by mediating PER2 and BMAL1 binding within the nucleus. This interaction is essential for organizing the functional mammalian circadian transcriptional complex.

Area of Science:

  • Molecular Biology
  • Chronobiology
  • Cell Biology

Background:

  • The BMAL1/CLOCK heterodimer forms the core of the mammalian circadian transcriptional complex.
  • PER2 and CRY1 are known repressors of this complex through direct interactions.
  • Previous work indicated PER2's altered localization in PML-deficient cells.

Purpose of the Study:

  • To investigate the role of PML in the localization and interaction of BMAL1, CLOCK, and PER2.
  • To elucidate the mechanism by which PML influences the circadian transcriptional complex formation.
  • To understand PML's contribution to nuclear organization of the circadian clock.

Main Methods:

  • Multi-color immunofluorescence (IF) staining.
  • Co-immunoprecipitation (co-IP) assays.
  • Analysis in wild-type (WT) and knockout (Pml(-/-), Bmal1(-/-)) mouse embryonic fibroblasts (MEFs), including those with mutant PML (K487R).

Main Results:

  • PML deficiency resulted in nuclear BMAL1 and cytosolic CLOCK.
  • WT PML facilitated nuclear co-localization of PER2 and BMAL1.
  • Mutant K487R PML sequestered BMAL1 and PER2 in the cytosol.
  • Cytosolic CLOCK and PER2 showed distinct staining patterns in Bmal1(-/-) MEF.

Conclusions:

  • PML mediates PER2 binding to BMAL1, crucial for forming the BMAL1/CLOCK heterodimer.
  • PML is essential for organizing a functional circadian clock complex within the nucleus.
  • BMAL1 plays a significant role in promoting the nuclear localization of CLOCK.

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