EFFECTS OF MODULATORS OF TYROSINASE ACTIVITY ON EXPRESSION OF MURINE INTERLEUKIN-2 CDNA DRIVEN BY THE TYROSINASE PROMOTER

Sequence analysis of the promoter region of the murine tyrosinase gene identified various consensus motifs including AP2 sites, cAMP and TPA response elements (CREs/TREs) and retinoic acid response element (RAR E) half-sites. By linking two different promoter lengths (2.5 kb or 76 9 bp) to murine interleukin-2 (IL-2) cDNA we have used IL-2 production by transduced B16 cells to monitor response to inducing agents capabl e of acting through these elements, Aminophylline or theophylline (0.1 -2 mM) added to the culture medium of transfected B16, but not 3T3, ce lls, increased IL-2 secretion significantly (P > 0.05) in a dose-depen dent fashion. This response was comparable in cells transfected with e ither the full length or the truncated promoter. Therefore, the cAMP r esponsiveness of the tyrosinase promoter probably is mediated by CREs and not AP2 sites, since the truncated promoter contains the former bu t not the latter regions. Retinoic acid at various concentrations (0.1 -1 mu M) evoked a standard increase in IL-2 production. Responses were similar for both promoter constructs, which suggests either that each RARE half-site can confer the full retinoic acid response, or that re tinoic acid is mediating its effect through pathways independent of th e RARE sites. TPA (2 nM-2 mu M) had no effect on IL-2 production. Thes e results demonstrate that the tyrosinase promoter can be induced by c ertain pharmacological agents and raise the possibility that administr ation of such substances may enhance expression of therapeutic genes c ontrolled by this promoter.