UVB IRRADIATION INDUCES CHANGES IN CELLULAR-LOCALIZATION AND PHOSPHORYLATION OF MOUSE HSP27

We investigated the induction, cellular localization and phosphorylati on of a low-molecular weight stress protein (heat shock protein 27, HS P27) by UVB (290-320 mn, max, 312 nm) irradiation stress using immunob lot and indirect immunofluorescence analysis in in vivo and in vitro e xperiments. The HSP27 was constitutively expressed and distributed in the cytoplasmic fraction of Pam 212 cells (mouse keratinocyte Line) or dorsal skin, The increase in the cytoplasm HSP27 level induced by UVB irradiation was less than two-fold that in nonirradiated controls. On the other hand, the translocation of HSP27 from cytoplasm to the nucl eus or perinuclear area was time- and dose-dependently induced by UVB irradiation, After WE irradiation, three isoforms having different iso electric points were detected in nucleic HSP27 by two-dimensional immu noblotting. The most basic isoform was the unphosphorylated type and t he two acidic isoforms were phosphorylated, suggesting that HSP27 is p hosphorylated in response to UVB irradiation and accumulates in or aro und the nucleus as a phosphorylated isoform, These results suggest tha t the translocation and phosphorylation of HSP27 are induced in respon se to UVB-irradiation stress.