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Background
HSF1 (HEAT-SHOCK TRANSCRIPTION FACTOR 1), also called HEAT-SHOCK FACTOR 1, is a protein that in humans is encoded by the HSF1 gene. The product of HSF1 gene is a heat-shock transcription factor. The International Radiation Hybrid Mapping Consortium maps the HSF1 gene to chromosome 8. HSF1 exists as an inactive monomer in a complex with Hsp40/Hsp70 and Hsp90. Upon stress, such as elevated temperature, HSF1 is released from the chaperone complex and trimerizes. HSF1 is then transported into the nucleus where it is hyperphosphorylated and binds to DNA containing heat shock elements. HSF1's target genes include major inducible heat shock proteins such as Hsp72, and interestingly, noncoding RNA within Satellite III repeat regions. In a novel in vitro system human HSF1 can be activated by nonnative protein, heat, and geldanamycin. HSR1 is constitutively expressed in human and rodent cells and its homologs are functionally interchangeable. Furthermore, Hsf1-deficient mice had a longer free-running period than wildtype littermates.