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The kinase DYRK1A phosphorylates the transcription factor FKHR at Ser329 in vitro, a novel in vivo phosphorylation

Y L Woods1, G Rena, N Morrice

  • 1MRC Protein Phosphorylation Unit, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK. y.l.woods@dundee.ac.uk

The Biochemical Journal
|April 20, 2001
PubMed

Insights

A novel phosphorylation site (Serine 329) on Forkhead in rhabdomyosarcoma (FKHR) was identified. This site, phosphorylated by DYRK1A, reduces FKHR

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Transcription Factor Regulation

Background:

  • Forkhead in rhabdomyosarcoma (FKHR) is a transcription factor involved in insulin signaling and apoptosis.
  • FKHR activity is regulated by phosphorylation at specific residues (Thr24, Ser256, Ser319) via the PI3K/PKB pathway, leading to nuclear exclusion and inactivation.

Purpose of the Study:

  • To identify novel phosphorylation sites on FKHR.
  • To investigate the functional consequences of FKHR phosphorylation at Serine 329.
  • To identify the kinase responsible for FKHR phosphorylation at Serine 329.

Main Methods:

  • Phosphorylation site mapping in HEK-293 cells.
  • In vitro kinase assays using purified rabbit skeletal muscle kinase.
  • Co-immunoprecipitation and subcellular localization studies.

Main Results:

  • A novel in vivo phosphorylation site, Serine 329, was identified on FKHR.
  • Phosphorylation at Serine 329 decreases FKHR's transactivation ability and nuclear presence.
  • DYRK1A (dual-specificity tyrosine-phosphorylated and regulated kinase 1A) was identified as the specific kinase for FKHR at Serine 329.
  • FKHR and DYRK1A were found to co-localize within the nucleus.

Conclusions:

  • DYRK1A phosphorylates FKHR at Serine 329, modulating its transcriptional activity and subcellular localization.
  • This phosphorylation event is distinct from the PKB-mediated pathway and occurs independently of IGF-1 stimulation.
  • DYRK1A represents a novel regulator of FKHR function in vivo.

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