MOLELCULAR BIOLOGY OF PHOTOTRANSDUCTION

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We have characterized the S-antigen genes from human and mouse, 33K protein genes from mouse and human, and a Shuzin gene from human. The gene sequences of the human and mouse S-antigens were determined. The S-antigen genes were approximately 50 kbp in length, contained 16 exons and 15 introns, and comprised 97% intron and 3% exon. The 5'-flanking regions of the genes, approximately 1.5 kbp long, had no known regulatory elements for transcription such as TATA, GC, or CCAAT boxes. The 5'- flanking regions of the human, cow, and mouse genes expressed tissue specific promoter activity in both the in vitro and in vivo transcription assays as well as in transgenic mice. Two genes of the 33K protein from human and mouse were isolated, and their DNA sequences were determined. Their genes were approximately 10 kbp in length. contained four exons and three introns. The gene of 33K protein seems to represent a family of genes and to have at least three genes with similar sequences. The functional role of the retinal protein Shuzin is unknown. Several cDNA's were isolated. Those from human and cow were sequenced, and the entire gene sequence of human Shuzin was determined. This gene, which is composed of two introns and three exons, has a highly repetitive sequence in the 5'-noncoding region. We have constructed fusion genes containing a 5'-flanking S-antigen gene sequence upstream of the bacterial gene chloramphenicol acetyl transferase (CAT) and microinjected a hybrid gene containing the 5'- flanking region of the mouse S-antigen gene and the CAT gene into transgenic mice. Those mice expressed CAT activity in the retina and pineal gland, suggesting that the 1,300 bp-long S-antigen promoter segment contains sufficient information to direct appropriate tissue- specific gene expression in transgenic mice. In addition, S-antigen was found in the lens fiber and epithelial cells, the cerebellum, and the cerebral cortex. These results indicated that S-antigen is expressed in a wider spectrum of cell types than previously recognized.