UV irradiation upregulates Egr-1 expression at transcription level

UVC irradiation rapidly and strongly induces protein expression of the earl y growth response-1 gene (Egr-1) encoding a transcription factor which may have a protective function against UV damage. In this paper, we further inv estigate mechanisms responsible for such induction. We show that UVC irradi ation also induced Egr-1 mRNA expression, increased transcription rate by n uclear run-on assay and stimulated Egr-1 promoter activity by CAT assay. Th e Egr-1 mRNA stability remained unchanged in UVC-treated cells. On the othe r hand, UVC irradiation slightly extended Egr-1 protein half-life. The indu ction of Egr-1 by UVC was observed in many different cell types. UVA and UV B also strongly induced Egr-1 expression. These results indicate that UVC r egulates Egr-1 expression at transcription level. The induction pattern of Egr-1 by UV suggests the importance of Egr-1 in the UV response.. (C) 1999 Wiley-Liss, Inc.