TET1 is controlled by pluripotency-associated factors in ESCs and downmodulated by PRC2 in differentiated cells and tissues

Abstract

Ten-eleven translocation (Tet) genes encode for a family of hydroxymethylase enzymes involved in regulating DNA methylation dynamics. Tet1 is highly expressed in mouse embryonic stem cells (ESCs) where it plays a critical role the pluripotency maintenance. Tet1 is also involved in cell reprogramming events and in cancer progression. Although the functional role of Tet1 has been largely studied, its regulation is poorly understood. Here we show that Tet1 gene is regulated, both in mouse and human ESCs, by the stemness specific factors Oct3/4, Nanog and by Myc. Thus Tet1 is integrated in the pluripotency transcriptional network of ESCs. We found that Tet1 is switched off by cell proliferation in adult cells and tissues with a consequent genome-wide reduction of 5hmC, which is more evident in hypermethylated regions and promoters. Tet1 downmodulation is mediated by the Polycomb repressive complex 2 (PRC2) through H3K27me3 histone mark deposition. This study expands the knowledge about Tet1 involvement in stemness circuits in ESCs and provides evidence for a transcriptional relationship between Tet1 and PRC2 in adult proliferating cells improving our understanding of the crosstalk between the epigenetic events mediated by these factors.

TET-Catalyzed 5-Hydroxymethylation Precedes HNF4A Promoter Choice during Differentiation of Bipotent Liver Progenitors

“…In addition, studies should explore the mechanisms behind TET1 overexpression at the early stage of differentiation. Fitting with our observations, overexpression of TET1 was recently described as a response to cell confluence and/or inhibition of cell proliferation (Neri et al., 2015). In our hands, HepaRG progenitors reduce their mitotic index 48 times after only 1 week of differentiation, as assessed by counting the percentage of mitotic nuclei with DAPI staining (data not shown).…”

SUMOylation coordinates BERosome assembly in active DNA demethylation during cell differentiation

“…Due to the branched structure of SUMO-conjugated proteins, modification with a single SUMO can give rise to a migration shift in gel electrophoresis higher than the 10 kDa expected from the molecular weight of SUMO peptides. A main source of oxidative DNA attack in unperturbed mESCs is the action of the highly expressed TET1 and TET2 proteins (Koh et al, 2011;Neri et al, 2015;Zhang et al, 2016), as indicated by relatively high levels of the oxidative 5mC derivatives, 5-hydroxymethyl-C (5hmC), 5fC and 5caC in such cells (Fig 4D). Exposure of mESC to H 2 O 2 induced a significant enrichment of < 150-kDa XRCC1 conjugates (Fig 1F), suggesting that XRCC1, like TDG, can be modified by DNA lesions generated by general oxidative stress.…”

“…Exposure of mESC to H 2 O 2 induced a significant enrichment of < 150-kDa XRCC1 conjugates ( Fig 1F), suggesting that XRCC1, like TDG, can be modified by DNA lesions generated by general oxidative stress. A main source of oxidative DNA attack in unperturbed mESCs is the action of the highly expressed TET1 and TET2 proteins (Koh et al, 2011;Neri et al, 2015;Zhang et al, 2016), as indicated by relatively high levels of the oxidative 5mC derivatives, 5-hydroxymethyl-C (5hmC), 5fC and 5caC in such cells ( Fig 4D). High levels of full-length TET1 protein and its shorter isoform TET1s ( Fig 1G) in ESCs also correlated with higher steady-state levels of XRCC1-SUMO in comparison with mouse embryonic fibroblasts (MEFs; Fig 1D and G), indicating that TET-dependent base oxidation may promote XRCC1 SUMOylation.…”

An epigenetic switch repressing Tet1 in gonadotropes activates the reproductive axis

“…TET1 is at its highest levels in ES cells (ESCs) and is down-regulated during differentiation. TET2 is also expressed in ESCs, and transcription of both genes is regulated by the pluripotency factors (9,10). Despite this, both TET1 and TET2 are also expressed through largely unknown mechanisms in differentiated tissues, although mice lacking TET1 or TET2 are viable and, asides from the TET2 effects on hematopoiesis, their definitive roles are mostly not clear (11)(12)(13).…”