rs13420827 — DNMT3A

DNMT3A rs13420827 — A Regulatory Switch in the Epigenome's Master Writer

Your DNA sequence is only half the story. The other half is the epigenome — the system of chemical tags that determines which genes get expressed and when. DNMT3A (DNA methyltransferase 3 alpha) is one of the principal enzymes that writes these tags, adding methyl groups¹¹ methyl groups
A methyl group (–CH₃) attached to the cytosine base creates 5-methylcytosine, which silences gene expression without altering the underlying DNA sequence to cytosines throughout the genome. rs13420827 lies in the 3' untranslated region (3' UTR) of DNMT3A — a stretch of mRNA that controls how efficiently the cell produces DNMT3A protein — and may subtly tune the global output of this critical methylation enzyme.

The Mechanism

rs13420827 is located at chromosome 2, position 25,231,098 (GRCh38), in the 3' UTR of DNMT3A. The plus-strand reference allele is C; the alternate allele is G. DNMT3A is transcribed from the minus strand, so in the mRNA context the variant appears in the 3' untranslated tail. The 3' UTR²² 3' UTR
The region after the stop codon in an mRNA; it contains binding sites for microRNAs and RNA-binding proteins that control transcript stability and translation efficiency is a hotspot for post-transcriptional regulation: binding sites for microRNAs and RNA-binding proteins that stabilize or destabilize the transcript. A C-to-G change in this region can create or destroy such binding sites, subtly altering how much DNMT3A protein each cell produces. No functional luciferase or reporter assay has been published for rs13420827 specifically — the mechanism is inferred from the variant's location and its epidemiological associations.

DNMT3A is responsible for de novo methylation: placing new methyl marks on previously unmethylated cytosines, particularly during early development, hematopoiesis, and adult tissue maintenance. It draws its methyl groups from SAM (S-adenosylmethionine), the universal methyl donor synthesized from methionine by the one-carbon cycle. Any variant that alters DNMT3A expression therefore shifts the enzymatic demand for SAM and interacts with the adequacy of the folate-B12 methylation pathway.

The Evidence

The clearest functional signal comes from a one-carbon pathway study in ovarian cancer³³ one-carbon pathway study in ovarian cancer
Kelemen LE et al. Genetic variation in the one-carbon transfer pathway and ovarian cancer risk. Cancer Research, 2008 in 829 cases and 941 controls. Among women who took multivitamin supplements, the G allele was associated with reduced ovarian cancer risk (OR 0.8, 95% CI 0.6–1.0; p interaction=0.006). The interaction specifically with multivitamin use — and not in non-users — suggests the variant's effect is conditioned on the availability of folate and B-vitamins that sustain DNMT3A's substrate pool. This is consistent with a model in which the G allele modestly reduces DNMT3A output, and adequate methyl-donor supply partially compensates.

In gastric cancer, findings have been mixed. A case-control study in Southern China⁴⁴ case-control study in Southern China
Yang XX et al. Risk-association of DNA methyltransferases polymorphisms with gastric cancer in the Southern Chinese population. Int J Mol Sci, 2012 found rs13420827 associated with reduced gastric cancer risk under the overdominant model (OR 0.66, 95% CI 0.45–0.97, p=0.034) in 242 cases and 294 controls. A separate Chinese case-control study⁵⁵ case-control study
Zhou J et al. Association of five genetic variations in DNMT1 and DNMT3A with gastric cancer in a Chinese population. Future Oncology, 2018 found the CG/GG genotypes associated with reduced cancer risk in individuals aged ≤60, and with reduced risk of poorly differentiated or advanced-stage tumors. However, a meta-analysis covering 13 studies⁶⁶ meta-analysis covering 13 studies
Li H et al. DNMT1, DNMT3A and DNMT3B Polymorphisms Associated With Gastric Cancer Risk. EBioMedicine, 2016 (3,959 cases / 5,992 controls) found rs13420827 not significantly associated with overall gastric cancer risk. The gastric cancer evidence for this specific SNP is therefore inconsistent and should be considered emerging at best.

In a Mexican seroepidemiological study⁷⁷ seroepidemiological study
Vargas-Alarcón G et al. Helicobacter pylori infection and DNMT3a polymorphism are associated with premature coronary artery disease and subclinical atherosclerosis. Microbiol Pathog, 2022 of 561 premature coronary artery disease patients and 599 controls, individuals carrying the GG genotype together with H. pylori infection showed a significant interaction on subclinical atherosclerosis risk (p interaction=1.1×10⁻⁵). This gene-environment interaction suggests the G allele may alter methylation of inflammation-related genes in the context of chronic bacterial infection.

A neurological study in Machado-Joseph disease⁸⁸ Machado-Joseph disease
Ding D et al. Polymorphisms in DNA methylation-related genes are linked to the phenotype of Machado-Joseph disease. Neurobiol Aging, 2019 found rs13420827 associated with earlier age-of-onset (p=0.019) in 613 patients with this CAG-repeat expansion disorder. DNMT3A influences CAG repeat stability through methylation of repeat-flanking sequences, so a variant affecting DNMT3A expression may shift the threshold for repeat expansion.

Practical Actions

The actionable implications of rs13420827 center on the same methyl-donor pathway that governs all DNMT3A function. Because DNMT3A uses SAM as its methyl-group donor, ensuring adequate folate and B12 intake is particularly relevant — especially given the ovarian cancer study's finding that the G allele's effect was specifically modified by multivitamin use. G allele carriers should prioritize active, pre-methylated forms of these vitamins to maximize methyl-donor availability without relying on enzymatic conversion steps that may themselves be polymorphic (e.g., MTHFR C677T).

The H. pylori interaction found in the cardiovascular study also suggests that CG and GG carriers may benefit from monitoring for and treating H. pylori infection, given the interaction with DNMT3A methylation capacity on atherosclerosis risk.

Interactions

The most relevant interaction is with MTHFR C677T (rs1801133). MTHFR supplies 5-methyltetrahydrofolate for homocysteine remethylation to methionine, the direct precursor of SAM. Individuals carrying both reduced-function MTHFR and the G allele at rs13420827 face a dual constraint: reduced SAM supply plus possibly altered DNMT3A expression. The companion DNMT3A variant rs11683424 (an intronic variant with stress-response and immune associations) sits in the same gene and may compound any functional shift in DNMT3A activity.

The Kelemen 2008 study explicitly framed rs13420827 within the one-carbon transfer pathway, alongside MTHFR, MTRR (rs1801394), and SLC19A1 (rs1051266), highlighting that this variant's risk modification is pathway-contextual: its effects depend on how well the rest of the folate-methionine cycle is functioning.