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The basic helix-loop-helix/PAS factor Sim is associated with hsp90. Implications for regulation by interaction with

J McGuire1, P Coumailleau, M L Whitelaw

  • 1Department of Medical Nutrition, Karolinska Institute, Huddinge, Sweden.

The Journal of Biological Chemistry
|December 29, 1995
PubMed

Insights

Sim, a Drosophila transcription factor, associates with the molecular chaperone hsp90. Dimerization with partners like Arnt or Per releases hsp90, potentially regulating Sim

Area of Science:

  • Developmental biology
  • Molecular biology
  • Genetics

Background:

  • Sim is a Drosophila developmental transcription factor with a basic helix-loop-helix (bHLH) and Per-Arnt-Sim (PAS) domain.
  • The bHLH/PAS dioxin receptor, structurally similar to Sim, is regulated by the chaperone hsp90 and dimerization with Arnt.
  • Understanding Sim's regulation is crucial for deciphering developmental pathways.

Purpose of the Study:

  • To investigate the association of Sim with the molecular chaperone hsp90.
  • To determine the role of dimerization partners, Arnt and Per, in regulating Sim-hsp90 interaction.
  • To elucidate the mechanism by which hsp90 influences Sim function.

Main Methods:

  • Biochemical assays to demonstrate Sim-hsp90 association.
  • Dimerization studies using Sim with Arnt and Per.
  • Analysis of hsp90 release upon Sim dimerization.

Main Results:

  • Sim was found to be stably associated with hsp90, similar to the dioxin receptor.
  • Dimerization of Sim with Arnt efficiently disrupted the Sim-hsp90 interaction, requiring Arnt's bHLH and PAS domains.
  • Dimerization with Per also led to hsp90 release from Sim.
  • The dioxin receptor did not interact with Sim.

Conclusions:

  • Hsp90 likely plays a role in the conditional regulation of Sim's function.
  • Per and other bHLH/PAS factors may activate Sim by inducing hsp90 release during dimerization.
  • This mechanism highlights a novel regulatory pathway for developmental transcription factors.

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