Human Telomerase Reverse Transcriptase (hTERT) Transcription Requires Sp1/Sp3 Binding to the Promoter and a Permissive Chromatin Environment.
The transcription of human telomerase gene hTERT is regulated by transcription factors (TFs), including Sp1 family proteins, and its chromatin environment. To understand its regulation in a relevant chromatin context, we employed bacterial artificial chromosome reporters containing 160 kb of human genomic sequence containing the hTERT gene. Upon chromosomal integration, the bacterial artificial chromosomes recapitulated endogenous hTERT expression, contrary to transient reporters. Sp1/Sp3 expression did not correlate with hTERT promoter activity, and these TFs bound to the hTERT promoters in both telomerase-positive and telomerase-negative cells. Mutation of the proximal GC-box resulted in a dramatic decrease of hTERT promoter activity, and mutations of all five GC-boxes eliminated its transcriptional activity. Neither mutations of GC-boxes nor knockdown of endogenous Sp1 impacted promoter binding by other TFs, including E-box-binding proteins, and histone acetylation and trimethylation of histone H3K9 at the hTERT promoter in telomerase-positive and -negative cells. The result indicated that promoter binding by Sp1/Sp3 was essential, but not a limiting step, for hTERT transcription. hTERT transcription required a permissive chromatin environment. Importantly, our data also revealed different functions of GC-boxes and E-boxes in hTERT regulation; although GC-boxes were essential for promoter activity, factors bound to the E-boxes functioned to de-repress hTERT promoter.
From the Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, Washington 99210.
De
D
Cheng
the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, and.
Yuanjun
Y
Zhao
From the Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, Washington 99210.
Shuwen
S
Wang
the School of Life Sciences and Technology, Tongji University, Shanghai 200092, China.
Wenwen
W
Jia
the School of Life Sciences and Technology, Tongji University, Shanghai 200092, China.
Jiuhong
J
Kang
From the Department of Pharmaceutical Sciences, Washington State University College of Pharmacy, Spokane, Washington 99210, the Department of Cellular and Molecular Physiology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania 17033, and jiyue.zhu@wsu.edu.
Jiyue
J
Zhu
D002460:Cell Line; D002843:Chromatin / Q000378:metabolism*; D006801:Humans; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016329:Sp1 Transcription Factor / Q000378:metabolism*; D051705:Sp3 Transcription Factor / Q000378:metabolism*; D019098:Telomerase / Q000235:genetics*; D014158:Transcription, Genetic
D002843:Chromatin; D016329:Sp1 Transcription Factor; D051705:Sp3 Transcription Factor; C509186:TERT protein, human; D019098:Telomerase
bacterial artificial chromosomes (BAC); chromatin immunoprecipitation (ChIP); chromatin regulation; chromatin-dependent gene regulation; gene repression; gene silencing; gene transcription; specificity protein 1 (Sp1); telomerase reverse transcriptase (TERT); transcription