Isolation of a clone partially encoding hill kangaroo X-linked hypoxanthine phosphoribosyltransferase: Sex differences in methylation in the body of the gene

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Abstract
An X-linked clone encoding exons 4–9 of the hypoxanthine phosphoribosyltransferase (HPRT) gene was isolated from a kangaroo (Macropus robustus: Marsupialia) λEMBL4 genomic library. Sequence similarity between the kangaroo and eutherian HPRT coding sequences was high; however, intron sizes varied significantly between the kangaroo and other eutherian species. HpaII and HhaI sites in the body of the gene were generally hypermethylated in vivo on the active, relative to the inactive X, with sites within intron 3 showing essentially complete correspondence of activity with methylation and inactivity with unmethylation. At approximately 5 kb downstream from the gene, a switch to unmethylation of active X-linked sites occurred. This switch occurred within a cluster of HpaII and HhaI sites that may represent a CG island associated with a subsequent gene.