Role of Tet proteins in enhancer activity and telomere elongation
- 1Howard Hughes Medical Institute, Boston Children’s Hospital, Boston, Massachusetts 02115, USA;
- 2Program in Cellular and Molecular Medicine, Boston Children’s Hospital, Boston, Massachusetts 02115, USA;
- 3Division of Hematology/Oncology, Department of Pediatrics, Boston Children’s Hospital, Boston, Massachusetts 02115, USA;
- 4Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA;
- 5Harvard Stem Cell Institute, Boston, Massachusetts 02115, USA
- Corresponding author: yzhang{at}genetics.med.harvard.edu
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↵6 These authors contributed equally to this work.
Abstract
DNA methylation at the C-5 position of cytosine (5mC) is one of the best-studied epigenetic modifications and plays important roles in diverse biological processes. Iterative oxidation of 5mC by the ten-eleven translocation (Tet) family of proteins generates 5-hydroxymethylcytosine (5hmC), 5-formylcytosine (5fC), and 5-carboxylcytosine (5caC). 5fC and 5caC are selectively recognized and excised by thymine DNA glycosylase (TDG), leading to DNA demethylation. Functional characterization of Tet proteins has been complicated by the redundancy between the three family members. Using CRISPR/Cas9 technology, we generated mouse embryonic stem cells (ESCs) deficient for all three Tet proteins (Tet triple knockout [TKO]). Whole-genome bisulfite sequencing (WGBS) analysis revealed that Tet-mediated DNA demethylation mainly occurs at distally located enhancers and fine-tunes the transcription of genes associated with these regions. Functional characterization of Tet TKO ESCs revealed a role for Tet proteins in regulating the two-cell embryo (2C)-like state under ESC culture conditions. In addition, Tet TKO ESCs exhibited increased telomere–sister chromatid exchange and elongated telomeres. Collectively, our study reveals a role for Tet proteins in not only DNA demethylation at enhancers but also regulating the 2C-like state and telomere homeostasis.
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Footnotes
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Supplemental material is available for this article.
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Article published online ahead of print. Article and publication date are online at http://www.genesdev.org/cgi/doi/10.1101/gad.248005.114.
- Received June 26, 2014.
- Accepted August 25, 2014.
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