Browsing by Author "Ma, Ding"

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    Analysis of KLF4 regulated genes in cancer cells reveals a role of DNA methylation in promoter- enhancer interactions
    (Taylor & Francis, 2018) Oyinlade, Olutobi; Wei, Shuang; Kammers, Kai; Liu, Sheng; Wang, Shuyan; Ma, Ding; Huang, Zhi-yong; Qian, Jiang; Zhu, Heng; Wan, Jun; Xia, Shuli; Medical and Molecular Genetics, School of Medicine
    Recent studies have revealed an unexpected role of DNA methylation at promoter regions in transcription activation. However, whether DNA methylation at enhancer regions activates gene expression and influences cellular functions remains to be determined. In this study, by employing the transcription factor krÜppel-like factor 4 (KLF4) that binds to methylated CpGs (mCpGs), we investigated the molecular outcomes of the recruitment of KLF4 to mCpGs at enhancer regions in human glioblastoma cells. First, by integrating KLF4 ChIP-seq, whole-genome bisulfite sequence, and H3K27ac ChIP-seq datasets, we found 1,299 highly methylated (β >0.5) KLF4 binding sites, three-quarters of which were located at putative enhancer regions, including gene bodies and intergenic regions. In the meantime, by proteomics, we identified 16 proteins as putative targets upregulated by KLF4-mCpG binding at enhancer regions. By chromosome conformation capture (3C) analysis, we demonstrated that KLF4 bound to methylated CpGs at the enhancer regions of the B-cell lymphocyte kinase (BLK) and Lim domain only protein 7 (LMO7) genes, and activated their expression via 3D chromatin loop formation with their promoter regions. Expression of mutant KLF4, which lacks KLF4 ability to bind methylated DNA, or removal of DNA methylation in enhancer regions by a DNA methyltransferase inhibitor abolished chromatin loop formation and gene expression, suggesting the essential role of DNA methylation in enhancer-promoter interactions. Finally, we performed functional assays and showed that BLK was involved in glioblastoma cell migration. Together, our study established the concept that DNA methylation at enhancer regions interacts with transcription factors to activate gene expression and influence cellular functions.
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    Targeting UDP-α-D-glucose 6-dehydrogenase inhibits glioblastoma growth and migration
    (Springer Nature, 2018-05) Oyinlade, Olutobi; Wei, Shuang; Lai, Bachchu; Laterra, John; Zhu, Heng; Goodwin, C. Rory; Wang, Shuyan; Ma, Ding; Wan, Jun; Xia, Shuli; Medical and Molecular Genetics, School of Medicine
    UDP-glucose 6-dehydrogenase (UGDH) produces UDP-α-D-glucuronic acid, the precursors for glycosaminoglycans (GAGs) and proteoglycans of the extracellular matrix. Elevated GAG formation has been implicated in a variety of human diseases, including glioblastoma (GBM). In our previous study, we found that Krüppel-like factor 4 (KLF4) promotes GBM cell migration by binding to methylated DNA, mainly methylated CpGs (mCpG) and transactivating gene expression. We identified UDGH as one of the downstream targets of KLF4-mCpG binding activity. In this study, we show that KLF4 upregulates UGDH expression in a mCpG-dependent manner, and UGDH is required for KLF4-induced cell migration in vitro. UGDH knockdown decreases GAG abundance in GBM cells, as well as cell proliferation and migration in vitro. In intracranial xenografts, reduced UGDH inhibits tumor growth and migration, accompanied by a decrease in the expression of extracellular matrix proteins such as tenascin C, brevican. Our studies demonstrate a novel DNA methylation-dependent UGDH upregulation by KLF4. Developing UGDH antagonists to decrease the synthesis of extracellular matrix components will be a useful strategy for GBM therapy.