A regulatory potential of the Xist gene promoter in vole M. rossiaemeridionalis.

X chromosome inactivation takes place in the early development of female mammals and depends on the Xist gene expression. The mechanisms of Xist expression regulation have not been well understood so far. In this work, we compared Xist promoter region of vole Microtus rossiaemeridionalis and other mammalian species. We observed three conserved regions which were characterized by computational analysis, DNaseI in vitro footprinting, and reporter construct assay. Regulatory factors potentially involved in Xist activation and repression in voles were determined. The role of CpG methylation in vole Xist expression regulation was established. A CTCF binding site was found in the 5' flanking region of the Xist promoter on the active X chromosome in both males and females. We suggest that CTCF acts as an insulator which defines an inactive Xist domain on the active X chromosome in voles.