|[Frontiers in Bioscience 1, a16-24, January 1, 1996]|
REGULATION OF INVOLUCRIN GENE EXPRESSION BY CALCIUM IN NORMAL HUMAN KERATINOCYTESDean C. Ng, Mei-Jhy Su, Richard Kim, and Daniel D. Bikle.
Endocrine Unit, VA Medical Center, University of California, 4150 Clement Street, 111N, San Francisco, CA 94121.
Received 12/7/95; Accepted 12/29/95; On-line 1/1/96
Calcium is essential for normal epidermal differentiation. Data from Northern and nuclear run-on analysis indicate that involucrin gene transcription is induced by 1.2 mM extracellular calcium. A 3.7 Kbp fragment of the involucrin gene, which contains 2.5 Kbp of upstream region, the transcription start site, and the first intron, was sub-cloned into the pGL3-basic luciferase reporter vector and transfected into pre-confluent normal human keratinocytes (NHK). The stimulated activities of this clone were above basal levels and was further enhanced eight-fold by 1.2 mM extracelluar calcium. The results from a series of truncation and internal deletion experiments revealed multiple calcium-independent enhancer elements between -2476 and -2131 bp of the transcription start site and a calcium-dependent element between -2131 and -2028 bp. This 103 bp fragment contains sequences of an AP-1 site (TGAGTCA), a SP-1 site (GGGCGG), and shares homology with two elements in the human keratin-1 promoter, within the regions identified as mediating the calcium responsiveness of that gene in keratinocytes. One or more of these putative elements may be involved in the calcium-dependent regulation of the involucrin gene transcription in NHK.