InterPro domain: IPR000232

Heat shock factor (HSF) is a transcriptional activator of heat shock genes [ 1 , 2 ]: it binds specifically to heat shock promoter elements, which are palindromic sequences rich with repetitive purine and pyrimidine motifs [ 3 ]. Under normal conditions, HSF is a homo-trimeric cytoplasmic protein, but heat shock activation results in relocalisation to the nucleus [ 3 ]. Each HSF monomer contains one C-terminal and three N-terminal leucine zipper repeats [ 4 ]. Point mutations in these regions result in disruption of cellular localisation, rendering the protein constitutively nuclear [ 5 ]. Two sequences flanking the N-terminal zippers fit the consensus of a bi-partite nuclear localisation signal (NLS). Interaction between the N- and C-terminal zippers may result in a structure that masks the NLS sequences: following activation of HSF, these may then be unmasked, resulting in relocalisation of the protein to the nucleus [ 5 ]. The DNA-binding component of HSF lies to the N terminus of the first NLS region, and is referred to as the HSF domain.

1. Molecular cloning and expression of a hexameric Drosophila heat shock factor subject to negative regulation. Cell 63, 1085-97
2. A novel mouse HSF3 has the potential to activate nonclassical heat-shock genes during heat shock. Mol. Biol. Cell 21, 106-16
3. Molecular cloning and expression of a human heat shock factor, HSF1. Proc. Natl. Acad. Sci. U.S.A. 88, 6906-10
4. Isolation of a cDNA for HSF2: evidence for two heat shock factor genes in humans. Proc. Natl. Acad. Sci. U.S.A. 88, 6911-5