METTL1-mediated m7G modification of valine tRNAs drives metabolic adaptation in pancreatic ductal adenocarcinoma cells
Jiabei Zhu, Qi Zhang, Douglas Evans, Rui Su, Qiuhui Pan, Ajay Goel
Jiabei Zhu, Qi Zhang, Douglas Evans, Rui Su, Qiuhui Pan, Ajay Goel
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Research Article Gastroenterology Oncology

METTL1-mediated m7G modification of valine tRNAs drives metabolic adaptation in pancreatic ductal adenocarcinoma cells

Abstract

Transfer RNA (tRNA) modifications play a critical role in regulating codon-specific mRNA translation and enabling tumor cell adaptation. The RNA methyltransferase 1 (METTL1) installs N7-methylguanosine (m7G) modifications on tRNAs, thereby shaping codon usage and translational output. However, the function and mechanistic contribution of the METTL1/tRNA axis in pancreatic ductal adenocarcinoma (PDAC) remain poorly defined. Here, we showed that METTL1 was overexpressed in PDAC tissues and that elevated METTL1 expression was associated with poor patient survival. Genetic ablation of METTL1 markedly suppressed PDAC cell proliferation, migration, and tumor growth in vitro and in vivo. Mechanistically, METTL1 loss selectively reduced m7G-modified valine tRNAs — particularly Val-AAC, Val-CAC, and Val-TAC — leading to impaired translation of valine-enriched OXPHOS transcripts. As a consequence, METTL1 deficiency disrupted mitochondrial respiration and energy production in PDAC cells. Consistent with this model, valine tRNA levels were elevated in PDAC tissues, and their selective depletion phenocopied METTL1 loss by impairing mitochondrial bioenergetics and tumor cell fitness. Thus, the METTL1/valine tRNA axis promoted PDAC progression through codon-dependent translational control of the mitochondrial electron transport chain and oxidative metabolism. Together, our findings identify a METTL1/tRNA/mitochondria signaling axis as a metabolic vulnerability and a promising therapeutic target in pancreatic cancer.

Authors

Jiabei Zhu, Qi Zhang, Douglas Evans, Rui Su, Qiuhui Pan, Ajay Goel

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Figure 3

METTL1 depletion reduces the levels of m7G-modified valine tRNAs by destabilizing them.

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METTL1 depletion reduces the levels of m7G-modified valine tRNAs by dest...
(A) Dot blot analysis of global m7G RNA modification levels in control and METTL1-KO groups from BxPC-3 and MiaPaCa-2 cells. (B and C) Densitometric quantification of m7G dot blot signals normalized to input RNA at each concentration in BxPC-3 (B) and MiaPaCa-2 (C) cells. **P < 0.01 and ***P < 0.001, by 2-tailed, unpaired t test. (D) Subset of m7G-modified tRNAs identified in human cells. (E–H) Relative expression of candidate tRNAs, Val-AAC (E), Val-CAC (F), Val-TAC (G), and Met-CAT (H) in control and METTL1-KO groups from BxPC-3 and MiaPaCa-2 cells by qRT-PCR. **P < 0.01 and ***P < 0.001, by 1-way ANOVA followed by Dunnett’s multiple-comparison test. (I and J) RIP assays with anti-METTL1 antibody or IgG control followed by qRT-PCR to detect valine tRNA enrichment in BxPC-3 (I) and MiaPaCa-2 (J) cells. **P < 0.01 and ***P < 0.001, by 2-tailed, unpaired t test. (K and L) The m7G modification of valine tRNAs was detected in the control and METTL1-KO groups from BxPC-3 (K) and MiaPaCa-2 (L) cells through MeRIP-qRT-PCR using an anti-m7G antibody. ***P < 0.001, by 1-way ANOVA, followed by Dunnett’s multiple-comparison test. (M–O) Relative expression of candidate tRNAs, Val-AAC (M), Val-CAC (N), and Val-TAC (O) by qRT-PCR in BxPC-3 and MiaPaCa-2 control and METTL1-KO cells treated with 5 μg/mL actinomycin D for the indicated durations. Data are representative of 3 independent experiments. All data are presented as the mean ± SD.