Heat-shock transcription factor that specifically binds heat shock promoter elements (HSE) (PubMed:22528049). 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 (PubMed:32061775, PubMed:33854238). In this process, may regulate denucleation of lens fiber cells in part by activating dnase1l1l and dnase2b transcription (PubMed:32061775). May be involved in DNA repair through the transcriptional regulation of rad51 (PubMed:22587838). May up-regulate TP53 protein in 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 (PubMed:31786107). Predominantly expressed in the eye. Expression in the ocular lens starts at as early as 24 hours post fertilization (hpf). In knockout animals, the eye lens grows normally, but during lens differentiation, denucleation is impaired and the degradation of mitochondria and endoplasmic reticulum is suppressed. Belongs to the HSF family.