TOBFAC: The database of tobacco transcription factors
Family: HSF
Minimum number of tobacco HSF genes: 34
Count of tobacco HSF sequences: 36
Pfam accession: HSF_DNA-bind
SHOULD possess HSF_DNA-bind domain
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.
Baniwal, SK; Bharti, K; Chan, KY; Fauth, M; Ganguli, A; Kotak, S; Mishra, SK; Nover, L; Port, M; Scharf, KD; Tripp, J; Weber, C; Zielinski, D; von Koskull-Döring, P. Heat stress response in plants: a complex game with chaperones and more than twenty heat stress transcription factors. J. Biosci. 2004 29(4):471-87 PMID: 15625403
Fujita, A; Kikuchi, Y; Kuhara, S; Misumi, Y; Matsumoto, S; Kobayashi, H. Domains of the SFL1 protein of yeasts are homologous to Myc oncoproteins or yeast heat-shock transcription factor. Gene 1989. 85(2):321-8 PMID: 2697640
Nover, L; Scharf, KD; Gagliardi, D; Vergne, P; Czarnecka-Verner, E; Gurley, WB. The Hsf world: classification and properties of plant heat stress transcription factors. Cell Stress Chaperones 1996. 1(4):215-23 PMID: 9222607
Wu, C. Heat shock transcription factors: structure and regulation. Annu. Rev. Cell Dev. Biol. 1995. 11:441-69 PMID: 8689565
Number of contigs: 32
Number of singlets: 4
Number of N terminal – 1
Number of C terminal – 2
Number of middle bits – 1
Number of full – 32
Total minimum number – 34
| Family | Genbank ID | Name |
Paul J Rushton
Marta T. Bokowiec
Xianfeng (Jeff) Chen
Thomas (Tom) W Laudeman
Jennifer F. Brannock
Michael P. Timko