International Mammalian Genome Society

logo18th International Mouse Genome Conference

17-22 October 2004, Seattle, USA


POSTER 50 - CHROMATIN DOMAINS THAT ESCAPE X INACTIVATION CHARACTERIZED BY CTCF BINDING AND HISTONE MODIFICATIONS

Cheng MK 1, Filippova GN 2, Disteche CM 1

1 University of Washington, Seattle, United States, 2 Fred Hutchinson Cancer Research Center, Seattle, United States

Genes that escape X inactivation are expressed in the context of inactive chromatin and must therefore employ some mechanism to overcome the repressive structure of the inactive X chromosome. One possible mechanism is binding of the chromatin insulator CTCF, which we hypothesize, acts as a boundary element between inactivated and escape regions on the X. We have found CTCF binding sites at the 5’ CpG islands of Jarid1c and Eif2s3x, two mouse genes that escape X inactivation and are adjacent to an inactivated gene. We have also shown that DNA methylation is very low at the CpG island of Jarid1c. To characterize the chromatin structure of transition regions, we are using chromatin immunoprecipitation and real-time PCR to map the status of histone H3 acetylation, histone H3 lysine 9 di-methylation, histone H3 lysine 27 tri-methylation, and histone H4 lysine 20 mono-methylation in the regions around and within the Jarid1c and Eif2s3x escape domains. We propose that CTCF binding at the boundaries between inactivated and escape domains inhibits the spread of epigenetic modifications characteristic of inactive chromatin such as DNA methylation and histone modifications.

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