Detection of differentially regulated genes in keratinocytes by cDNA array hybridization: Hsp27 and other novel players in response to artificial ultraviolet radiation

cDNA array technology was used to identify novel genes participating in the ultraviolet response of cultured human keratinocytes. cDNA arrays representing more than 50,000 different cDNA clones were hybridized with complex probes generated by SMART-polymerase chain reaction amplification of 150 ng of total RNA extracted 24 h after ultraviolet irradiation. Fifty-one clones with differential hybridization signals were detected, representing 19 different sequences; 10 known genes (seven ultraviolet induced, three ultraviolet suppressed) and further nine expressed sequence tags of unknown genes. In seven of 10 genes the data from cDNA arrays probed with SMART-cDNA could be confirmed by northern blot analysis. The 27 kDa heat shock protein mRNA was induced. Keratins 6 and 17, markers for the hyperproliferative status of keratinocytes, were among the ultraviolet suppressed genes. The change of expression profile of keratins indicates a differentiation towards a phenotype of keratinocytes present in the suprabasal layers of the epidermis. These mechanisms may contribute to the ultraviolet protective function of the epidermis and to the anti-proliferative action of ultraviolet in the therapy of psoriasis. We also detected an induction of adenylyl cyclase associated protein and the suppression of G(s)alpha (a stimulating subunit of the trimeric membrane bound GTPase).