HSF Transcription Factor Family
Organisms respond to elevated temperatures and to chemical and physiological stresses by an
increase in the synthesis of heat shock proteins. The regulation of heat shock gene expression
in eukaryotes is mediated by the conserved heat shock transcription factor (HSF). HSF is present
in a latent state under normal conditions; it is activated upon heat stress by induction of
trimerization and high-affinity binding to DNA and by exposure of domains for transcriptional
activity. Analysis of HSF cDNA clones from many species has defined structural and regulatory
regions responsible for the inducible activities. The heat stress signal is thought to be
transduced to HSF by changes in the physical environment, in the activity of HSF-modifying
enzymes, or by changes in the intracellular level of heat shock proteins.
Heat shock factor (HSF) is a transcriptional activator of heat shock genes it binds specifically
to heat shock promoter elements, which are palindromic sequences rich with repetitive purine and
pyrimidine motifs. Under normal conditions, HSF is a homo-trimeric cytoplasmic protein, but heat
shock activation results in relocalisation to the nucleus. Each HSF monomer contains one
C-terminal and three N-terminal leucine zipper repeats. Point mutations in these regions result
in disruption of cellular localisation, rendering the protein constitutively nuclear. 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. The DNA-binding component of HSF lies
to the N-terminus of the first NLS region, and is referred to as the HSF domain.
64 predicted putative HSF TF peptide,
CDS, and cDNA sequences;
blast HSP, multiple sequence alignment in
Soy - TFKB.
64 HSF domain peptide sequences with alignment
and phylogeny tree .
29 HSF protein and DNA sequences with
annotations for soybean in PlantTFDB. Most are partial sequences.
Last updated by Dr. Jeff Chen on June 5, 2009.
