REGULATION OF INTERCELLULAR-ADHESION MOLECULE-1 EXPRESSION BY RETINOIC ACID - ANALYSIS OF THE 5' REGULATORY REGION OF THE GENE

Human intercellular adhesion molecule-1 (ICAM-1), a specific ligand fo r the lymphocyte-function-associated antigen-1, plays an important rol e in immune responses. ICAM-1 expression is regulated by various proin flammatory cytokines, by PMA, and by retinoic acid. In this study, we have investigated the mechanisms of transcriptional control involved i n the stimulation of ICAM-1 gene expression by retinoic acid in SK-N-S H cells. Northern-blot analysis demonstrated that ICAM-1 mRNA is maxim ally induced at 24 hr, suggesting that it is not an early-response gen e with respect to retinoic-acid responsiveness, whereas the retinoic a cid receptor-beta mRNA level was maximal 12 hr following retinoic acid treatment. To analyze the 5'-regulatory region of the ICAM-1 gene, an EcoRI/Sall fragment spanning the first 1.3 kb upstream of the transla tional state site was used to direct the expression of a linked lucife rase reporter gene in transient of transfected cells with 10 mu M reti noic acid resulted in a 10- to 13-fold increase in luciferase activity compared with untreated cells. Deletion mutant analysis revealed that a region located between -393 and -176 bp from the translational star t site is critical for retinoic acid stimulation of luciferase activit y. This region harbors a consensus sequence for a retinoic-acid-respon sive element (RARE) homologous to the element found upstream of the al cohol dehydrogenase-3 gene. Co-transfection of expression vectors enco ding the retinoic acid receptor-alpha, -beta. or -gamma, with reporter plasmids harboring the putative RARE, confirmed that the ICAM-1 gene is regulated by retinoic acid in a retinoic acid receptor-dependent fa shion. (C) 1994 Wiley-Liss, Inc.