Induction of the 72-kD heat shock protein in xeroderma pigmentosum complementation group A fibroblasts

In mammalian cells, 72-kD heat shock protein (HSP72) is the major stress-inducible protein that is thought to play a protective role against the various environmental stresses. In order to know the induction mechanism of HSP72, we examined the HSP72 in DNA repair-deficient xeroderma pigmentosum group A fibroblasts (XP2OSSV) and normal fibroblasts (WI38VA13) by the indirect immunofluorescence method using a monoclonal antibody specific for the inducible 72-kD protein. Heat-shock treatment of the same survival fraction (5% survival) induced HSP72 in xeroderma pigmentosum (XP) and normal cells. However, as compared with XP cells, normal cells showed the induction of HSP72 more rapidly and strongly. When XP and normal cells were irradiated with UVC at the same survival dose (10% survival), apparent induction of HSP72 was observed in both cell lines. In the case of UVC irradiation at the same dose (1.0 J/m2), though XP cells showed the induction of HSP72, HSP72 was not induced in normal cells. In both cell lines, heat-shock treatment caused more rapid induction of HSP72 than UV irradiation. These results suggest that the induction mechanism of HSP72 might be different between heat-shock treatment and UV irradiation. In addition, in the case of UV irradiation, the extent of DNA damage after DNA repair or the cell death might be involved in the induction of HSP72.