Augmented expression of HSP72 protein in normal human fibroblasts irradiated with ultraviolet light

Normal human fibroblasts synthesized heat shock protein (HSP) 72 constitutively and its expression was augmented 6 hours after UV irradiation. Maximum induction of HSP72 was obtained at 12 hours and HSP72 showed a punctuated distribution in nucleus. While unscheduled DNA synthesis was almost completed 12 hours after UV irradiation, the S phase fraction decreased immediately and recovered after 6 hours. Thus, HSP72 augmentation was occurred coincidentally with the recovery of S phase, and suggested that HSP72 had some function during the recovery of DNA replication inhibited after UV irradiation.