Loss of MYC and E-box3 binding contributes to defective MYCmediated transcriptional suppression of human MC-let-7a-1~let-7d in glioblastoma
Publication in refereed journal

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摘要Previously, we reported that MYC oncoprotein down-regulates the transcription of human MC-let-7a-1~let-7d microRNA cluster in hepatocarcinoma (HCC). Surprisingly, in silico analysis indicated that let-7 miRNA expression levels are not reduced in glioblastoma (GBM). Here we investigated the molecular basis of this differential expression. Using human GBM U87 and U251 cells, we first demonstrated that forced over-expression of MYC indeed could not down-regulate the expression of human MC-let-7a-1~let-7d microRNA cluster in GBM. Furthermore, analysis of MC-let-7a- 1~let-7d promoter in GBM indicated that MYC failed to inhibit the promoter activity. Pearson's correlation and Linear Regression analysis using the expression data from GSE55092 (HCC) and GSE4290 (GBM) demonstrated a converse relationship of MClet- 7a-1~let-7d and MYC only in HCC but not in GBM. To understand the underlying mechanisms, we examined whether MYC could bind to the non-canonical E-box 3 located in the promoter of MC-let-7a-1~let-7d. Results from both chromatin immuneprecipitation (ChIP) and super-shift assays clearly demonstrated the loss of MYC and E-box 3 binding in GBM, suggesting for the first time that a defective MYC and E-box3 binding in GBM is responsible for the differential MYC mediated transcriptional inhibition of MC-let-7a-1~let-7d and potentially other tumor suppressors. MYC and let-7 are key oncoprotein and tumor suppressor, respectively. Understanding the molecular mechanisms of their regulations will provide new insight and have important implications in the therapeutics of GBM as well as other cancers.
著者Wang Z., Lin S., Zhang J., Xu Z., Xiang Y., Yao H., Ge L., Xie D., Kung H.-F., Lu G., Poon W.S., Liu Q., Lin M.C.-M.
期刊名稱Oncotarget
出版年份2016
月份8
日期30
卷號7
期次35
出版社Impact Journals
出版地United States
頁次56266 - 56278
國際標準期刊號1949-2553
語言英式英語
關鍵詞Glioblastoma, MC-let-7a-1~let-7d, MYC, Transcriptional regulation

上次更新時間 2020-25-10 於 02:31