Ultraviolet-A-induced transactivation of the vascular endothelial growth factor gene in HaCaT keratinocytes is conveyed by activator protein-2 transcription factor.
Ultraviolet-A radiation represents a significant proportion of the ultraviolet solar spectrum that was recently shown to affect gene expression of epidermal keratinocytes by molecular mechanisms distinct from ultraviolet-B radiation. As ultraviolet-A either alone or in combination with ultraviolet-B may contribute to photocarcinogenesis, we aimed to explore the biologic effects of ultraviolet-A radiation on vascular endothelial growth factor gene expression by the immortalized keratinocyte cell line HaCaT. As keratinocyte-derived vascular endothelial growth factor not only provides the major cutaneous angiogenic activity but may also augment the malignant phenotype of tumor cells, we studied the molecular mechanisms of ultraviolet-A-induced vascular endothelial growth factor expression in HaCaT cells, serving as a transformed preneoplastic epithelial cell line. Whereas ultraviolet-B-mediated vascular endothelial growth factor expression has been previously indicated to be conveyed by indirect mechanisms, ultraviolet-A rapidly induced vascular endothelial growth factor mRNA expression in a fashion comparable to that seen with the transforming growth factor alpha, representing a direct and potent activator of vascular endothelial growth factor gene transcription. Ultraviolet-A was found to readily induce vascular endothelial growth factor promoter-based reporter gene constructs through a consensus element for activator protein-2 transcription factor. The critical role of activator protein-2 was substantiated by demonstration of ultraviolet-A-induced activator-protein-2-dependent nuclear DNA binding activity to this site, and by inhibition of ultraviolet-A-mediated vascular endothelial growth factor gene transcription through insertion of a critical mutation within the activator protein-2 sequence. Together, our data further elucidate photobiologic aspects of ultraviolet-A-induced gene expression by characterizing mechanisms of vascular endothelial growth factor upregulation at the molecular level. In addition, our experiments support the concept of a more general importance of activator protein-2 in ultra- violet-A-mediated responses by keratinocytes or keratinocyte-derived cell lines.
Gille
J
J
Zentrum der Dermatologie, Klinikum der J. W. Goethe-Universität, Frankfurt am Main, Germany. Gille@em.uni-frankfurt.de
Reisinger
K
K
Asbe-Vollkopf
A
A
Hardt-Weinelt
K
K
Kaufmann
R
R
D020029:Base Pairing; D002460:Cell Line / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000494:pharmacology*; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000235:genetics*; D020862:GC Rich Sequence; D005786:Gene Expression Regulation / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D015603:Keratinocytes; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics*; D020930:MAP Kinase Kinase Kinases / Q000502:physiology; D009154:Mutation; D010100:Oxygen / Q000494:pharmacology; D010777:Photochemistry; D011401:Promoter Regions, Genetic / Q000528:radiation effects; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics; D026082:Singlet Oxygen; D015534:Trans-Activators / Q000528:radiation effects; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics / Q000494:pharmacology*; D015533:Transcriptional Activation / Q000528:radiation effects; D014466:Ultraviolet Rays; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D004268:DNA-Binding Proteins; D016228:Endothelial Growth Factors; D008222:Lymphokines; D015534:Trans-Activators; D050656:Transcription Factor AP-2; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D026082:Singlet Oxygen; D020930:MAP Kinase Kinase Kinases; D010100:Oxygen