Mapping of loci and translocation breakpoints in Xq13: isolation of a conserved locus that maps close to CCG1 in human and mouse

MSG1 (melanocyte-specific gene 1): mapping to chromosome Xq13.1, genomic organization, and promoter analysis

MSG1 (melanocyte-specific gene 1) is a recently isolated gene predominantly expressed in cultured normal melanocytes and pigmented melanoma cells. MSG1 encodes a 27-kDa nuclear protein that has strong intrinsic transcriptional transactivating activity. In this report, the human MSG1 gene was mapped to chromosome Xq13.1 using X chromosome-specific somatic cell hybrids, and the mouse Msg1 gene was mapped 1.9 +/- 1.3 cM proximal to Xist using an interspecific backcross panel. Both the human and the mouse MSG1 genes consist of three exons and two introns within 5 kb of genomic DNA, and their genomic structures are highly conserved. Southern blot analysis suggests the existence of MSG1 homologues in chicken, zebrafish, and Drosophila. A 2.0-kb fragment of the 5'-flanking region of the mouse Msg1 gene contains a TATA box and potential binding sites for several transcription factors including USF, Brn-3, Brn-2, TFE3, Oct-1, AP-2, and Spl. This promoter fragment activates transcription of a reporter gene in pigmented melanoma cells, but not in amelanotic melanoma cells or nonmelanocytic cells, indicating that Msg1 expression is at least partially regulated at the transcriptional level.