Probing Keratinocyte and Differentiation Specificity of the Human K5 Promoter In Vitro and in Transgenic Mice

The study investigated the regulatory mechanisms of the human K5 gene expression in keratinocytes, both in vitro and in transgenic mice. It was found that 6,000 base pairs of the K5 promoter directed specific expression in basal cells of stratified epithelia, while a truncated 90 bp promoter still targeted expression to stratified epithelia, particularly in the epidermis, hair follicles, and tongue. However, this truncated promoter showed some deviations in expression patterns. Protein-DNA interaction studies revealed that keratinocyte nuclear proteins binding to the K5 gene segment from -90 to +32 bp played a role in transcriptional regulation. These proteins were shared with the K14 promoter but differed from previously identified keratinocyte-specific factors. Mutagenesis indicated that factors near the TATA box and transcription initiation site were crucial for the cell type specificity of the truncated promoter.