Coactivation of AP-1 activity and TGF-beta1 gene expression in the stress response of normal skin cells to ionizing radiation.
Activation of the AP-1 transcription factor and TGF-beta1 growth factor by ionizing radiation was studied both in vivo in pig skin, and in vitro in human fibroblasts and keratinocytes. Three and 6 h after irradiation, the Fos and Jun proteins and their binding activity to an AP-1 consensus sequence were strongly induced by high doses of gamma-rays. c-Fos, c-Jun and JunB proteins were found to be present in gel-shift complexes by probing with specific antibodies. Both keratinocytes and fibroblasts exhibited heightened AP-1 activity following irradiation. As we previously found that TGF-beta1 is involved in the development of skin lesions induced by radiation, TGF-beta1 gene expression was also examined. Two and 6 h after irradiation, the levels of TGF-beta1 transcripts were increased in skin. By immunostaining, TGF-beta1 protein levels were found to be increased in fibroblasts, keratinocytes and endothelial cells. As the TGF-beta1 promoter contains AP-1 binding sites, the relation between AP-1 activity and TGF-beta1 induction was addressed. The -365 TGF-beta1 promoter fragment, which contains a high affinity AP-1 site, exhibited increased binding to Jun and Fos proteins following irradiation. These results suggest that stress-inducible TGF-beta1 expression is mediated by the activation of AP-1 transcription factor.
Martin
M
M
Laboratoire de Radiobiologie et d'Etude du Génome, CEA, DVS, Gif sur Yvette, France.
Vozenin
M C
MC
Gault
N
N
Crechet
F
F
Pfarr
C M
CM
Lefaix
J L
JL
D000818:Animals; D002478:Cells, Cultured; D016384:Consensus Sequence; D004307:Dose-Response Relationship, Radiation; D015870:Gene Expression / Q000528:radiation effects; D006801:Humans; D018384:Oxidative Stress; D011401:Promoter Regions, Genetic; D012867:Skin / Q000378:metabolism / Q000528:radiation effects*; D013552:Swine; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000096:biosynthesis* / Q000235:genetics
D018808:Transcription Factor AP-1; D016212:Transforming Growth Factor beta