HSF4: ProductsHSF4 (heat shock factor 4) is a 53 kDa member of the HSF family of transcription factors. It is highly expressed in the lens where it maintains lens integrity and blocks FGF synthesis. Human HSF4 has two isoforms HSF4B and HSF4A. Human HSF4B is 493 amino acids in length. It contains one DNA binding region (aa 18-122) and two hydrophobic repeat domains A/B and C (aa 130-204 and 369-390). HSF4B activates transcription, whereas, HSF4A represses transcription. HSF4A shows a 45 aa substitution for aa 246-320. Over aa 309-463, human HSF4B shares 73% aa sequence identity with mouse HSF4B.