Abstract 2864: Acetylation regulates TET2 stability and enzymatic activity

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA DNA methylation, one of the key epigenetic modifications in the mammalian genome, plays fundamental roles in development and disease. Although DNA methylation and DNA methyltransferases (DNMTs) have been studied intensively, our knowledge about DNA demethylation is just starting to emerge. The Ten-eleven translocation (TET) family of proteins are newly identified methylcytosine dioxygenases/demethylases that can oxidize 5-methylcytosine (5mC) to 5-hydroxymethylcytosine (5hmC), and promote DNA demethylation either passively through DNA replication, or actively via thymine DNA glycosylase (TDG)-mediated base excision repair. TET-mediated DNA demethylation has also been shown to play important roles in diverse biological processes and tumorigenesis. Human TET2 is frequently mutated in myeloid malignancies, while loss of 5hmC and TETs expressions have been broadly observed in many other cancer types. Recent studies suggested that TETs may be regulated by microRNAs and calpain proteases, but, overall, the regulation of TET activities is not well outlined. Here we show, in human ovarian cancer cells, that TET2 activity may be significantly modulated by post-translational modifications. TET2 is acetylated by p300/CBP at K110/111, and this acetylation can be reversed by HDAC1/2 and SIRT1/2 deacetylases. Acetylation increases TET2 stability by protecting it from ubiquitination and proteasome-mediated degradation. Interestingly, DNMT1 physically associates with and stabilizes TET2 protein, and a TET2 acetylation deficient mutant (2KR) disrupts this association, indicating that acetylation of TET2 may stimulate DNMT1 binding which prevents TET2 from degradation. In addition, we show that acetylation increases TET2 enzymatic activity. Treatment of cells with HDAC inhibitors TSA/NAM, or knocking down HDAC1/2, significantly increases global 5hmC levels. Consistent with these latter observations, the 2KR mutant almost completely abolishes TET2 catalytic activity, and this mutant protein is less efficient in forming dimer with wild type TET2. Thus acetylation events may increase the activity of TET2 through enhanced dimerization of the protein. Taken together, our study reveals a novel acetylation-dependent regulatory mechanism controlling the function of TET2. Citation Format: Yang Zhang, Yi Cai, Wenbing Xie, Hariharan Easwaran, Stephen B. Baylin. Acetylation regulates TET2 stability and enzymatic activity. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2864. doi:10.1158/1538-7445.AM2015-2864