Nucleobase Modifiers Identify TET Enzymes as Bifunctional DNA Dioxygenases Capable of Direct N-Demethylation |
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Authors: | Dr. Uday Ghanty Tong Wang Dr. Rahul M. Kohli |
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Affiliation: | 1. Department of Medicine, Department of Biochemistry and Biophysics, University of Pennsylvania, Philadelphia, PA, 19104 USA;2. Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania, Philadelphia, PA, 19104 USA |
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Abstract: | TET family enzymes are known for oxidation of the 5-methyl substituent on 5-methylcytosine (5mC) in DNA. 5mC oxidation generates the stable base 5-hydroxymethylcytosine (5hmC), starting an indirect, multi-step process that ends with reversion of 5mC to unmodified cytosine. While probing the nucleobase determinants of 5mC recognition, we discovered that TET enzymes are also proficient as direct N-demethylases of cytosine bases. We find that N-demethylase activity can be readily observed on substrates lacking a 5-methyl group and, remarkably, TET enzymes can be similarly proficient in either oxidation of 5mC or demethylation of N4-methyl substituents. Our results indicate that TET enzymes can act as both direct and indirect demethylases, highlight the active-site plasticity of these FeII/α-ketoglutarate-dependent dioxygenases, and suggest activity on unexplored substrates that could reveal new TET biology. |
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Keywords: | DNA methylation enzymes epigenetics nucleic acids TET enzymes |
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