Expression of tyrosinase gene introduced into the albino mouse embryo.

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Tyrosinase is a copper containing monooxygenase and is known as the key enzyme for melanin biosynthesis in pigment cells. Deficiency in the enzme activity results in albinism.An attempt was made in the present sutdy to express mouse tyrosinase cDNAs in albino melanocytes. A cDNA library was constructed from poly(A)^+mRNA from mouse melanocytes and screened using anti-tyrosinase antibody and oligonucleotide probes whith corresponded to amino acid sequence of tyrosinase. The first cloned cDNA for tyrosinase was 1838 bp long (designated tyrs-33) and was found to encode a protein of 51 kDa. The second cdNA clone (Tyrs-J) was 1978 kbp and contained an open reading frame which encoded a protein of 60 kDa.On the other hand, 5' non-coding region was screened from a genomic DNA library derived from mouse embryo. A clone, G3L, was about 4.8 kbp long and was shown to contain the first exon (819 bp) and 5' non-coding sequence. In the putative regulatory sequence of the 5' non-coding region, two sets of promoter-like structure consisting of TATA box and CCAAT box. In order to examine the expressibility of these cDNAs and the function of the regulatory region, we fused the cDNAs with the 5' non-coding region and transfected into cultured melanocytes from albino mouse. One of the fused genes, 5' sequence-Tyrs-J, was found to express in the cells and to direct melanin production.