Interferon--mediated Inactivation of Transcription of the 230-kDa Bullous Pemphigoid Antigen Gene (BPAG1) Provides Novel Insight into Keratinocyte Differentiation

Abstract Interferon- (IFN-) has been shown to regulate epidermal keratinocyte growth and differentiation. In this study, we examined the effects of recombinant human IFN- on the expression of the gene encoding the 230-kDa bullous pemphigoid antigen (BPAG1), a marker of the mitotic basal cell phenotype in the epidermis. Northern analysis revealed a dose- and time-dependent suppression of BPAG1 expression by IFN- in cultured human keratinocytes from several different donors, and incubation of the cells with IFN- in the presence of cycloheximide demonstrated that this effect required ongoing protein synthesis. The inhibition of BPAG1 gene expression was also demonstrated at the protein level by indirect immunofluorescence using a monoclonal antibody recognizing the human 230-kDa bullous pemphigoid antigen. Transient transfections of cultured keratinocytes with BPAG1 promoter-chloramphenicol acetyltransferase reporter gene plasmids indicated marked suppression of the promoter activity by IFN-, and deletion constructs were able to identify a defined region containing the responsive element (IFN- inhibitory element). Reduced transcription of the BPAG1 gene by IFN- was also demonstrated by in vitro nuclear run-on assays. These data, which indicate inactivation of transcription of a basal keratinocyte-specific gene (BPAG1) by IFN-, provide novel insight into the mechanisms of IFN--mediated keratinocyte gene regulation and epidermal differentiation in inflammatory diseases.