Regulation of Drosophila heat shock factor trimerization: global sequence requirements and independence of nuclear localization

Mol Cell Biol. 1996 Dec;16(12):7018-30. doi: 10.1128/MCB.16.12.7018.

Abstract

Heat shock transcription factor (HSF) is a multidomain protein that exists as a monomer under normal conditions and is reversibly induced upon heat shock to a trimeric state that binds to DNA with high affinity. The maintenance of the monomeric state is dependent on hydrophobic heptad repeats located at the amino- and carboxy-terminal regions which have been proposed to form an intramolecular coiled-coil structure. In a systematic deletion analysis to identify other regions of HSF that may be required to regulate its oligomeric state, we have found that local sequences encompassing the carboxy-terminal end of the DNA binding domain and a broad region of HSF between the heptad repeats also contribute to this regulation. Immunocytochemical analysis of mutant HSF proteins revealed a canonical motif required for nuclear localization. HSF proteins lacking the nuclear localization signal remain in the cytoplasm, but these HSFs nonetheless exhibit reversible heat stress-inducible trimerization. The results indicate that the signals that regulate HSF trimerization operate in both the nuclear and cytoplasmic compartments of the cell.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Biological Transport
  • Cell Nucleus / genetics
  • Drosophila / genetics*
  • Heat-Shock Proteins / genetics*
  • Mutation
  • Signal Transduction / genetics*

Substances

  • Heat-Shock Proteins