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The doubletime and CKII kinases collaborate to potentiate Drosophila PER transcriptional repressor activity

Pipat Nawathean1, Michael Rosbash

  • 1Howard Hughes Medical Institute, Biology Department MS 008, Brandeis University, 415 South Street, Waltham, MA 02454, USA.

Molecular Cell
|February 5, 2004
PubMed

Insights

The circadian rhythm in Drosophila is regulated by PER protein phosphorylation. This process enhances PER

Area of Science:

  • Circadian Biology
  • Molecular Genetics
  • Drosophila melanogaster research

Background:

  • Circadian rhythms are governed by negative feedback loops in gene expression across model organisms.
  • In Drosophila, the delay between clock protein synthesis and function is hypothesized to involve phosphorylation-regulated nuclear entry.

Purpose of the Study:

  • To investigate the interplay between PER protein phosphorylation, nuclear localization, and transcriptional repression in Drosophila S2 cells.
  • To elucidate the role of PER kinases DBT and CKII in regulating the circadian clock mechanism.

Main Methods:

  • Assaying the relationship between PER phosphorylation, nuclear localization, and transcriptional repression in cultured S2 cells.
  • Utilizing kinase inhibition and PER nuclear export inhibition to dissect regulatory pathways.
  • Analyzing the impact of phosphorylation on PER's direct repression activity and nuclear localization.

Main Results:

  • DBT and CKII kinases collaborate to phosphorylate PER, thereby increasing its repression activity.
  • Phosphorylation directly enhances PER repression activity, independent of nuclear export.
  • PER nuclear localization appears to be an indirect outcome of active PER binding to DNA or chromatin.

Conclusions:

  • Circadian regulation of PER nuclear localization in flies is primarily driven by alterations in PER transcriptional activity.
  • The findings challenge the prevailing model where nuclear import/export directly dictates PER's circadian role.
  • This study provides a refined understanding of post-translational modifications in circadian clock regulation.

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