Reactivation of an inactive human X chromosome: Evidence for X inactivation by DNA methylation

T. Mohandas, R. S. Sparkes, L. J. Shapiro

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    A mouse-human somatic cell hybrid clone, deficient in hypoxanthine-guanine phosphoribosyltransferase (HPRT) and containing a structurally normal inactive human X chromosome, was isolated. The hybrid cells were treated with 5-azacytidine and tested for the reactivation and expression ofhuman X-linked genes. The frequency of HPRT-positive clones after 5-azacytidine treatment was 1000-fold greater than that observed in untreated hybrid cells. Fourteen independent HPRT-positive clones were isolated and analyzed for the expression of human X markers. Isoelectric focusing showed that the HPRT expressed in these clones is human. One of the 14 clones expressed human glucose-6-phosphate dehydrogenase and another expressed human phosphoglycerate kinase. Since 5-azacytidine treatment results in hypomethylation of DNA, DNA methylation may be a mechanism of human X chromosome inactivation.

    Original languageEnglish
    Pages (from-to)393-396
    Number of pages4
    Issue number4480
    StatePublished - 1981


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