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Epigenetic modifications play important roles in both cancer and aging, and studying the mechanisms
of epigenetics would deepen our understanding of both cancer and aging. Dr. Cheng’s project focuses
on examining the role of epigenetics in X chromosome inactivation. Human Xp11.2 is a region that
contains a 285 kb domain of multiple genes that escape X inactivation. Located at one end of this
domain is the gene SMCX. The same region in mouse contains many homologous genes but only one of
them, Smcx, escapes X inactivation. CTCF binding sites and elevated levels of acetylated histone H3
were previously found by the lab to be associated with the 5’ end of mouse Smcx, suggesting that
CTCF may protect one end of the escape domain in mouse. In contrast, no CTCF binding was observed
at the 5’ end of human SMCX, which is adjacent to a gene that also escapes inactivation. These data
suggested that boundary elements that separate chromatin domains might be repositioned in different
species. Dr. Cheng is searching for CTCF binding, increased histone H3 acetylation, and other
epigenetic modifications on the human and mouse X chromosomes in regions that separate the escape
domain from the adjacent inactive chromatin using chromatin immunoprecipitation and quantitative
PCR.
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