HUMAN INTEGRIN BETA(3) GENE-EXPRESSION - EVIDENCE FOR A MEGAKARYOCYTIC CELL-SPECIFIC CIS-ACTING ELEMENT

The human integrin beta(3) participates in a wide range of adhesive bi ologic functions and is expressed in a selected subset of tissues, but little is known about the cis-acting DNA elements or trans-acting fac tors responsible for this regulation. Using cell lines characterized f or beta(3) expression, a number of upstream regulatory regions in the beta(3) gene were identified. (1) The three regions from -1159 to -584 , -290 to -146, and -126 to -115 demonstrated positive, negative, and negative activity, respectively. (2) The region from -115 to +29 of th e beta(3) gene was sufficient for cell-specific activity. Deletion of the sequence from -115 to -89 produced a 6- to 40-fold reduction in re porter gene activity in beta(3)-expressing megakaryocytic cell lines ( K562, Dami, and MEL), but only a 1.7- and 2.7-fold reduction, respecti vely, in beta(3)-expressing endothelial and melanoma cell lines, and 1 .3- and 2.8-fold reduction, respectively, in non-beta(3)-expressing Ch inese hamster ovary and 293 cell lines. This sequence also bound nucle ar proteins in a cell-specific manner in electrophoretic mobility shif t assays. Mutational analysis indicated that the sequence GAGGGG (posi tions -113 to -108) is a megakaryocytic cell line-specific cis-acting element. (3) The region from -89 to +29 promoted lower activity in all cell lines. We also provide evidence that a CCCACCC sequence at posit ion -70 has transcriptional activity, most likely through the Spl tran scription factor. These data supply the first detailed map of the tran scriptional regulatory elements of the 5' region of the beta(3) gene, define positive regulatory sequences with potent megakaryocyte prefere ntial activity, and indicate that the ubiquitous transcription factor, Sp1, may augment beta(3) gene expression. (C) 1998 by The American So ciety of Hematology.