TRANSCRIPTIONAL ANALYSIS OF THE 5'-NONCODING REGION OF THE HUMAN INVOLUCRIN GENE

Human involucrin whose gene transcription is directed by a 2456-nucleo tide (nt) 5'-noncoding region is a structural component of the epithel ial cornified layer, Transient transfection assays demonstrated that t his region is transcriptionally active in multiplying keratinocytes an d is enhanced by 2 mM CaCl2 treatment, Calcium-independent transcripti onal activity and the interaction with the AP-1 transcriptional factor was located on the proximal part (nt -159 to -1) of the 5'-noncoding region. However, CaCl2 responsiveness was mapped to a distal 1185-nt f ragment (nt -2456 to -1272), Moreover, this fragment potentiated the H erpes simplex thymidine kinase promoter in normal keratinocytes and is responsive to calcium treatment in a cell type-specific manner, Inter estingly, the absence of a 491-nt fragment located between the two enh ancer domains (nt -651 to -160) resulted in transcriptional activation in multiplying keratinocytes. This fragment interacts with AP-1 and t he YY1 transcriptional silencer, It is concluded that human involucrin 5'-noncoding region contains at least three regulatory domains, a dis tal CaCl2-responsive enhancer, a putative transcriptional silencer (th at interacts with AP-1 and YY1), and a proximal enhancer/promoter (tha t interacts with AP-1), Thus, this study demonstrates the presence of particular transcriptional factors can potentially regulate the human involucrin expression.