Epigenetic characterization of CXXC5 gene locus

Kars, Gizem
17β-estradiol (E2), the main circulating form of estrogen, induces diverse cellular responses through Estrogen Receptor α and β (ERα and ER β). E2 signaling mediates physiology and pathophysiology of several tissues by regulating E2 responsive genes. Previous studies of our laboratory described a noval E2 responsive gene, CXXC5 that is regulated through ERα. CXXC5 is a member of Zinc Finger CXXC domain protein family. Like other members of family, CXXC5 appears to function as epigenetic factor, co-regulator or transcription factor. Also several studies indicate that CXXC5 is a poor prognostic factor in tissue malignancies including breast cancer which shows high dependency to E2 signaling. Thus, understanding the transcription of CXXC5 is important. Despite the importance, transcriptional regulation of CXXC5 has not been understood and mechanism of E2 mediated expression of CXXC5 has not been explored. It is known that E2 regulated gene expression involves dynamic interaction of transcription factors and epigenetic modifiers. Consequently, several epigenetic alterations of DNA including methylation, chromatin structure or histone modifications are critical components of gene expressions. Here, we aimed to test epigenetic features of CXXC5 locus and effects of E2, at possible regulatory sites. Initially we carried out in silico analysis to define putative promoter of CXXC5. Then we conducted DNA methylation and nucleosome profiling for the promoter and for previously identified enhancer region of CXXC5 in MCF7 cells in the absence or presence of E2. Our studies suggest that CXXC5 has a CpG Island (CGI) promoter which is dramatically hypomethylated independently from E2. While the enhancer region and exon 2 as gene body is hypermethylated. Moreover, we detected a nucleosome free subregion at 5’ of the CXXC5 exon 1, in the untreated cells. The Enhancer region was identified as occupied independently from E2. In summary, although general description of epigenetic features of CXXC5 regulatory regions has been identified in our study, detailed mechanism of E2 regulation could be explained by further studies.


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Citation Formats
G. Kars, “Epigenetic characterization of CXXC5 gene locus,” M.S. - Master of Science, Middle East Technical University, 2018.