title: Dual roles of c-Myc in the regulation of hTERT gene.
abstract: Human telomerase gene hTERT is important for cancer and aging. hTERT promoter is regulated by multiple transcription factors (TFs) and its activity is dependent on the chromatin environment. However, it remains unsolved how the interplay between TFs and chromatin environment controls hTERT transcription. In this study, we employed the recombinase-mediated BAC targeting and BAC recombineering techniques to dissect the functions of two proximal E-box sites at -165 and +44 nt in regulating the hTERT promoter in the native genomic contexts. Our data showed that mutations of these sites abolished promoter binding by c-Myc/Max, USF1 and USF2, decreased hTERT promoter activity, and prevented its activation by overexpressed c-Myc. Upon inhibition of histone deacetylases, mutant and wildtype promoters were induced to the same level, indicating that the E-boxes functioned to de-repress the hTERT promoter and allowed its transcription in a repressive chromatin environment. Unexpectedly, knockdown of endogenous c-Myc/Max proteins activated hTERT promoter. This activation did not require the proximal E-boxes but was accompanied by increased promoter accessibility, as indicated by augmented active histone marks and binding of multiple TFs at the promoter. Our studies demonstrated that c-Myc/Max functioned in maintaining chromatin-dependent repression of the hTERT gene in addition to activating its promoter.
authors.affiliation: Department of C & M Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA.
authors.forename: Yuanjun
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of C & M Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, Washington, USA.
authors.forename: De
authors.initials: D
authors.lastname: Cheng
authors.affiliation: Department of C & M Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, Washington, USA.
authors.forename: Shuwen
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of C & M Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, Washington, USA jiyue.zhu@wsu.edu.
authors.forename: Jiyue
authors.initials: J
authors.lastname: Zhu
mesh_terms: D002460:Cell Line; D002843:Chromatin / Q000378:metabolism; D022202:Chromosomes, Artificial, Bacterial; D004268:DNA-Binding Proteins / Q000378:metabolism; D024721:E-Box Elements; D005786:Gene Expression Regulation; D006657:Histones / Q000378:metabolism; D006801:Humans; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism / Q000502:physiology*; D034741:RNA, Small Interfering / Q000378:metabolism; D019098:Telomerase / Q000096:biosynthesis / Q000235:genetics*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation
chemical_list: D002843:Chromatin; D004268:DNA-Binding Proteins; D006657:Histones; C489427:MYC protein, human; D016271:Proto-Oncogene Proteins c-myc; D034741:RNA, Small Interfering; D014157:Transcription Factors; C509186:TERT protein, human; D019098:Telomerase