TISSUE-SPECIFIC EXPRESSION OF MOUSE TYROSINASE GENE IN CULTURED CHICKEN-CELLS

A mouse tyrosinase cDNA has been combined with different promoters and inserted into several replication-competent avian leukosis proviruses and the viruses were transferred into cultured albino chick cells by viral infection. Expression of the tyrosinase gene depended on one of four promoter sequences: the resident constitutive promoter (Rous sarc oma virus long-terminal repeat; RSV-LTR), 471 bp from the mouse tyrosi nase gene-associated promoter, 519 bp from the Japanese quail tyrosina se gene associated promoter, or 369 bp from the quail tyrosinase promo ter. The infected cells expressed tyrosinase and produced pigment whic h could be seen with the light microscope. Immunofluorescence microsco py, using an anti mouse tyrosinase T1-specific antibody, also showed t he presence of mouse tyrosinase. When infected with the same viral tit er, gene expression was highest with the constitutive LTR promoter. Th e quail tyrosinase promoter, while less efficient than the LTR, was mo re efficient than the other tyrosinase promoter. Fibroblasts and hepat ocytes infected with the construct carrying the constitutive promoter or the truncated quail promoter expressed tyrosinase. The mouse and qu ail promoters appeared to show tissue-specific expression since fibrob lasts and hepatocytes infected with viruses carrying these promoters d id not express mouse tyrosinase. Toxicity is associated with constitut ive expression of tyrosinase in nonmelanocytes. Therefore the viruses that carry the tissue specific promoters should be useful for in vivo studies. (C) 1994 Academic Press, Inc.