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Updated: Jan 25, 2026

The Detection of 5-Hydroxymethylcytosine in Neural Stem Cells and Brains of Mice
Published on: September 19, 2019
TET enzymes augment activation-induced deaminase (AID) expression via 5-hydroxymethylcytosine modifications at the
Chan-Wang J Lio1, Vipul Shukla2, Daniela Samaniego-Castruita2
1Division of Signaling and Gene Expression, La Jolla Institute, San Diego, CA, USA. arao@lji.org lio@lji.org.
Abstract:
TET enzymes are dioxygenases that promote DNA demethylation by oxidizing the methyl group of 5-methylcytosine to 5-hydroxymethylcytosine (5hmC). Here, we report a close correspondence between 5hmC-marked regions, chromatin accessibility and enhancer activity in B cells, and a strong enrichment for consensus binding motifs for basic region-leucine zipper (bZIP) transcription factors at TET-responsive genomic regions. Functionally, Tet2 and Tet3 regulate class switch recombination (CSR) in murine B cells by enhancing expression of Aicda, which encodes the activation-induced cytidine deaminase (AID) enzyme essential for CSR. TET enzymes deposit 5hmC, facilitate DNA demethylation, and maintain chromatin accessibility at two TET-responsive enhancer elements, TetE1 and TetE2, located within a superenhancer in the Aicda locus. Our data identify the bZIP transcription factor, ATF-like (BATF) as a key transcription factor involved in TET-dependent Aicda expression. 5hmC is not deposited at TetE1 in activated Batf-deficient B cells, indicating that BATF facilitates TET recruitment to this Aicda enhancer. Our study emphasizes the importance of TET enzymes for bolstering AID expression and highlights 5hmC as an epigenetic mark that captures enhancer dynamics during cell activation.
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