Heat Shock Transcription Factor 4 (HSF4)

HSF4 is a novel member of the HSF family, rather than the human homolog of chicken HSF3. They reported that the HSF4 sequence encodes a 463-amino acid polypeptide. Northern blotting revealed that HSF4 is expressed as a 2.5-kb mRNA in the heart, skeletal muscle, and brain, and at much lower levels in some other tissues. HSF4 bound specifically to the heat-shock response element but repressed, rather than activated, transcription.

HSF4 lacks the carboxyl-terminal hydrophobic repeat which is shared among all vertebrate HSFs and has been suggested to be involved in the negative regulation of DNA binding activity. Two alternatively spliced transcripts encoding distinct isoforms and possessing different transcriptional activity have been described.