Functional analysis of the tyrosinase gene and brown-locus protein gene promoters

Tyrosinase is a rate-limiting enzyme of melanin biosynthesis and the brown (b)-locus protein is responsible for the formation of black melanin rather than brown. To identify the cis-acting element(s) required for pigment cell-specific gene transcription, we analyzed the promoter function of two pigment cell-specific genes encoding mouse tyrosinase and b-locus protein using a cell-free transcription system prepared from mouse melanoma cells. Functional and structural analysis of both gene promoters reveals that three elements are conserved in both genes at equivalent positions, suggesting that these elements may be responsible for pigment cell-specific transcription. We discuss possible mechanisms for pigment cell-specific expression of the tyrosinase and b-locus protein genes.