Gene family of male-specific testosterone 16 alpha-hydroxylase (C-P-450(16 alpha)) in mice. Organization, differential regulation, and chromosome localization.

Three genes in the testosterone 16 alpha-hydroxylase (C-P-450(16 alpha)) family, ca, cb, and cc, are characterized. The sizes of the genes are approximately 4.5 to 5.2 kilobase pairs, and all three consist of nine exons with junctions at identical sites. Gene ca is identified as the male-specific, androgen-dependent C-P-450(16 alpha) gene in adult mice, since the exonic sequence matched 100% to the cDNA, pc16 alpha-2 (Wong, G., Kawajiri, K., and Negishi, M. (1987) Biochemistry 26, 8683-8690). Gene cb and cc are organized in tandem within 18-kilobase pair DNA. Their encoded P-450s contain an approximate 94% nucleotide sequence similarity to the C-P-450(16 alpha). The high similarity in gene nucleotide sequences, including the introns and flanking regions, suggests a combination of an ancestral gene duplication and gene conversion as a mechanism for evolution of the C-P-450(16 alpha) family. Gene ca shows male-specific expression in mouse kidney as well as in liver; gene cb, neither sex-specific nor androgen-dependent, is seen only in liver; gene cc is not expressed in either adult mouse liver or kidney. Expression of these three genes is not detected in adult mouse lung. It appears, therefore, that the C-P-450(16 alpha) gene family includes a large number of genes whose expressions are differentially regulated. Southern hybridization of C-P-450(16 alpha) cDNA to genomic DNAs from mouse-hamster somatic hybrid cells localizes tentatively this gene family on mouse chromosome 15. The recombination frequency in BXD recombinant inbred mice suggests that the C-P-450(16 alpha) gene family is approximately 16M from the 55-kDa locus.

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