TRANSCRIPTIONAL REGULATORS OF EXPRESSION OF K-NUMBER-16, THE DISEASE-ASSOCIATED KERATIN

In most malignant and benign skin diseases, the normal pattern of kera tin expression is altered. Among other phenotypic changes, the express ion of hyperproliferation- and activation-associated keratins K#16 and K#6 is induced. Because the molecular mechanisms and the nuclear regu lators involved in this induction are unknown, we have characterized t he transcriptional regulators of expression of the keratin K#16 promot er. Our previous studies have shown that the transcription of K#16 is strongly and specifically induced in epidermal keratinocytes by epider mal growth factor (EGF), through the EGF-responsive element (RE). In t he present work, using an electrophoretic mobility-shift assay, we hav e found several nuclear protein binding sites that have been identifie d as an Sp1 site, an AP2 site, the EGF-RE, and an enhancer element. Th e function of each site was assessed in transfection assays using spec ific deletions. Both the Sp1 and EGF-RE sites are essential for K#16 p romoter activity. The site that functions as an independent enhancer, E, was found adjacent to and interacting with a sequence recognized by the AP2 transcription factor. This knowledge of the nuclear regulator s of expression of the disease-associated K#16 keratin provides insigh t into the molecular parameters that might be important in skin diseas es.