Photoactivated phytochrome induces rapid PIF3 phosphorylation prior to proteasome-mediated degradation

Mol Cell. 2006 Aug 4;23(3):439-46. doi: 10.1016/j.molcel.2006.06.011.

Abstract

Following light-induced nuclear translocation, specific members of the phytochrome (phy) photoreceptor family (phyA to phyE) interact with bHLH transcription factors, such as PIF3, and induce changes in target-gene expression. The biochemical mechanism comprising signal transfer from phy to PIF3 has remained undefined but results in rapid degradation of PIF3. We provide evidence that photoactivation of phy induces rapid in vivo phosphorylation of PIF3 preceding degradation. Both phyA and phyB redundantly induce this PIF3 phosphorylation, as well as nuclear speckle formation and degradation, by direct interaction with PIF3 via separate binding sites. These data suggest that phy-induced phosphorylation of proteins such as PIF3 may represent the primary intermolecular signaling transaction of the activated photoreceptor, tagging the target protein for proteosomal degradation, possibly in nuclear speckles.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Active Transport, Cell Nucleus / physiology
  • Alkaline Phosphatase / metabolism
  • Amino Acid Sequence
  • Apoproteins / genetics
  • Apoproteins / metabolism
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / radiation effects
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Basic Helix-Loop-Helix Transcription Factors / genetics
  • Basic Helix-Loop-Helix Transcription Factors / metabolism*
  • Binding Sites / genetics
  • Blotting, Western
  • Cell Nucleus / drug effects
  • Cell Nucleus / metabolism
  • Cell Nucleus / radiation effects
  • Leupeptins / pharmacology
  • Light
  • Mutation / genetics
  • Phosphorylation / drug effects
  • Phosphorylation / radiation effects
  • Phytochrome / genetics
  • Phytochrome / metabolism*
  • Phytochrome A / genetics
  • Phytochrome A / metabolism
  • Phytochrome B / genetics
  • Phytochrome B / metabolism
  • Plants, Genetically Modified
  • Protease Inhibitors / pharmacology
  • Proteasome Endopeptidase Complex / metabolism*
  • Proteasome Inhibitors
  • Protein Binding
  • Two-Hybrid System Techniques

Substances

  • Apoproteins
  • Arabidopsis Proteins
  • Basic Helix-Loop-Helix Transcription Factors
  • Leupeptins
  • PIF3 protein, Arabidopsis
  • Phytochrome A
  • Protease Inhibitors
  • Proteasome Inhibitors
  • Phytochrome
  • Phytochrome B
  • PHYD protein, Arabidopsis
  • Alkaline Phosphatase
  • Proteasome Endopeptidase Complex
  • benzyloxycarbonylleucyl-leucyl-leucine aldehyde