Regulation of human and mouse telomerase genes by genomic contexts and transcription factors during embryonic stem cell differentiation

Abstract

Differential regulation of telomerase reverse transcriptase (TERT) genes contribute to distinct aging and tumorigenic processes in humans and mice. To study TERT regulation, we generated mouse embryonic stem cell (ESC) lines containing single-copy bacterial artificial chromosome (BAC) reporters, covering hTERT and mTERT genes and their neighboring loci, via recombinase-mediated BAC targeting. ESC lines with chimeric BACs, in which two TERT promoters were swapped, were also generated. Using these chromatinized BACs, we showed that hTERT silencing during differentiation to embryoid bodies (EBs) and to fibroblast-like cells was driven by the human-specific genomic context and accompanied by increases of repressive epigenetic marks, H3K9me3 and H3K27me3, near its promoter. Conversely, the mouse genomic context did not repress TERT transcription until late during differentiation. The hTERT promoter was more active than its mouse counterpart when compared in the same genomic contexts. Mutations of E-box and E2F consensus sites at the promoter had little effect on hTERT transcription in ESCs. However, the mutant promoters were rapidly silenced upon EB differentiation, indicating that transcription factors (TFs) bound to these sites were critical in maintaining hTERT transcription during differentiation. Together, our study revealed a dynamic hTERT regulation by chromatin environment and promoter-bound TFs during ESC differentiation.

Engineering a humanized telomerase reverse transcriptase gene in mouse embryonic stem cells

“…Next, we determined whether the human genomic sequences conferred human-like TERT regulation in mouse cells. A subset of aforementioned BAC reporters were integrated into the same acceptor site in a mouse ESC line T2-5 by RMBT 11 . The TERT promoters in all the BAC reporters, M(wt), M(hPro), M(h5IR), M(h5IRI2), and M(h5IRI2I6), were highly active in ESCs as determined by ratios of Rluc / Fluc .…”

“…Our previous studies revealed that the hTERT gene was embedded in a condensed chromatin domain in somatic cells and inhibition of histone deacetylation led to an opening of this domain and activated hTERT transcription 10 . We have recently shown that repression of the hTERT promoter was dictated by distal elements and required a human specific genomic context 11,12 .…”

Therapeutics of Stem Cell Treatment in Anti-Aging and Rejuvenation

“…Epigenetic regulation is essential for establishing and maintaining stem cell function, and evidence suggests that epigenetic dysregulation leads to potential changes in stem cells during aging [18] [25] [26] [27]. The term epigenetics refers to changes in gene expression that do not involve changes in the underlying DNA sequence [28] [29].…”

Investigation of transcriptome mechanism associated with osteoporosis explored by microarray analysis

“…It is well-known that substantial genes were regulated by transcription factors (TFs), recognized as the master regulators binding to DNA sequences specifically and thereby modulating gene transcription. The transcriptional regulation elicited by TFs is of importance to normal function of the organism, with transcriptional regulation central to cell cycle growth and survive (2), cell differentiation (3), cell adhesion (4) and cell homeostasis (5). However, TF failure leads to nearly 1/3 of human developmental diseases ascribed to TF misregulations (6,7).…”