Identification of a DNA-binding protein (keratinocyte transcriptional protein-1) recognizing a keratinocyte-specific regulatory element in the 230-kDa bullous pemphigoid antigen gene.

We have recently cloned and characterized the entire human 230-kDa bullous pemphigoid antigen gene, which is expressed at a relatively high level in the basal keratinocytes. A putative AP2 binding sequence (KRE2), identified in the position -1786 to -1778, was cloned in front of a heterologous thymidine kinase chloramphenicol acetyltransferase construct, and transient transfections of normal human keratinocytes indicated a marked enhancement of the promoter activity. Normal human keratinocyte nuclear extracts contained a protein, designated as keratinocyte transcriptional protein-1 (KTP-1), which complexed with the KRE2 oligomer when examined by gel mobility shift assays. This protein was not detected in human skin fibroblast or HeLa cell nuclear extracts that did, however, contain AP2. UV cross-linking studies and Southwestern analyses suggested that KTP-1 binds to DNA as a single polypeptide of approximately 110 kDa. These data suggest that KTP-1 is a DNA-binding protein clearly distinct from AP2, and this protein may be responsible for the basal keratinocyte-specific expression of the bullous pemphigoid antigen gene.