Heat-shock transcription factor that specifically binds heat shock promoter elements (HSE) (PubMed:22587838, PubMed:23507146). Required for denucleation and organelle rupture and degradation that occur during eye lens terminal differentiation, when fiber cells that compose the lens degrade all membrane-bound organelles in order to provide lens with transparency to allow the passage of light (By similarity). In this process, may regulate denucleation of lens fiber cells in part by activating DNASE2B transcription (By similarity). May be involved in DNA repair through the transcriptional regulation of RAD51 (PubMed:22587838). May up-regulate p53/TP53 protein in eye lens fiber cells, possibly through protein stabilization (PubMed:28981088). In the eye lens, controls the expression of alpha-crystallin B chain/CRYAB and consequently may be involved in the regulation of lysosomal acidification (By similarity). Transcriptional repressor. Transcriptional activator. Homotrimer (By similarity). Exhibits constitutive DNA binding and forms trimers even in the absence of stress (By similarity). Interacts with ALKBH4, DUSP26, MAPK1, MAPK2, MAPK8 and MAP kinase p38 (PubMed:16581800, PubMed:23145062). Expressed in heart, skeletal muscle, eye and brain, and at much lower levels in some other tissues. Phosphorylated mainly on serine residues. Phosphorylation on Ser-298 promotes sumoylation on Lys-293. Isoform HSF4B is constitutively sumoylated. Sumoylation represses the transcriptional activity and is promoted by phosphorylation on Ser-298. HSFA is not sumoylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the HSF family. Leiden Open Variation Database (LOVD)