Molecular and genetic analysis of the mouse homolog of the Drosophila suppressor of position-effect variegation 3-9 gene

The Drosophila melanogaster gene suppressor of position-effect variegation 3-9 [Su(var)3-9] encodes a component of heterochromatin with a chromodomain and a SET domain. Here, we describe the cloning of a mouse homolog called Suv39h1 and describe the genomic organization, pattern of expression, and genetic map position. The genomic locus is approximately 10 kb and consists of five exons. The first two exons, 1a and 1b, are alternative first exons and are followed by three common exons. Two mRNAs, encompassing exon 1a or 1b, encode protein isoforms with distinct amino termini, but which are otherwise identical, including the chromodomain and SET domain. Interestingly, only one of the isoforms contains a putative nuclear localization signal. Consistent with other genes encoding proteins associated with chromatin structure, Suv39h1 is expressed in a widespread manner. Interspecific backcross mapping localized Suv39h1 near tattered (Td) and scurfy (sf) on the proximal X Chromosome (Chr). However, analysis of Td/Y and sf/Y mutant stocks indicated that Suv39h1 is not responsible for either mutant phenotype.