Keratinocyte transglutaminase promoter analysis - Identification of a functional response element

Keratinocyte transglutaminase catalyzes isopeptide bond formation to yield the highly insoluble crosslinked envelope during terminal differentiation of epidermal cells, Transcriptional response elements were identified in the 5'-flanking DNA of the gene for this enzyme by a combination of transient transfection and electrophoretic mobility shift analyses, Since human keratinocytes transcribed ineffectively transfected transglutaminase flanking DNA, a key feature of these experiments was the use of rat bladder epithelial cells as recipients, Serial deletion experiments identified by transient transfection an important response region containing three putative AP2-like response elements approximately 0.5 kilobases from the transcription initiation site, Oligonucleotides, each containing a single one of the elements, formed specific complexes with keratinocyte nuclear proteins, Two of the response elements were found to be functional by transfection in site-specific deletion experiments, Of these one formed specific DNA-protein complexes with nuclear proteins only from cells exhibiting keratinocyte differentiation. UV cross-linking experiments estimated the protein component of the complex to be approximate to 85 kDa, This response element alone increased substantially the transcription of a minimal transglutaminase promoter in transient transfections. Further characterization of the putative transcription factor binding to this response element may provide insight into the regulation of keratinocyte transglutaminase.