Project description:Quantitative and qualitative changes in mRNA translation occur in tumor cells and support cancer progression and metastasis. Post-transcriptional nucleoside modifications of transfer RNAs (tRNAs) at the wobble U34 base are highly conserved and contribute to translation fidelity. Here, we show that ELP3 and CTU1/2, partner enzymes in U34 mcm5s2-tRNA modification, are upregulated in human breast cancers and sustain metastasis. Elp3 genetic ablation strongly impaired invasion and metastasis formation in the PyMT model of invasive breast cancer. Mechanistically, ELP3 and CTU1/2 support cellular invasion through the translation of the oncoprotein DEK. As a result, DEK promotes the IRES-dependent translation of the pro-invasive transcription factor LEF1. Consistently, a DEK mutant, whose codon composition is independent of U34 mcm5s2-tRNA modification, escapes the ELP3- and CTU1-dependent regulation and restores the IRES-dependent LEF1 expression. Our results demonstrate the key role of U34 tRNA modification to support specific translation during breast cancer progression and highlight a functional link between tRNA modification- and IRES-dependent translation during tumor cell invasion and metastasis.analysis of transcriptomic changes due to Elp3genetic deletion in cells extracted from PyMT mammary tumors.
Project description:Treatment selections are very limited for patients with advanced nasopharyngeal carcinoma (NPC) experiencing disease progression. Uncovering the potential mechanism underlying NPC progression is crucial for identify novel treatments. Here we show that N7-methylguanosine (m7G) tRNA modification enzyme METTL1 and its partner WDR4 are significantly elevated in NPC and associated with poor prognosis. Loss-of-function and gain-of-function assays demonstrated that METTL1/WDR4 mediated m7G tRNA modification promotes NPC growth and metastasis in vitro and in vivo. Mechanistically, m7G tRNA modification selectively regulates the translation of transcripts with higher percentage of m7G tRNA decoded codons. Moreover, further analysis revealed that METTL1-mediated m7G tRNA modification activates WNT/β-Catenin signaling pathway to promote NPC cell epithelial-mesenchymal transition (EMT) and chemoresistance to cisplatin and docetaxel in vitro and in vivo. Our work uncovers a novel layer of mRNA translation regulation mechanism at codon recognition step mediated by tRNA modification and reveals the critical function of tRNA modification in cancer progression.
Project description:Radiofrequency heat ablation is an ideal radical cure for HCC treatment; however, insufficient radiofrequency ablation (IRFA) could lead to a high recurrence rate. N7-methylguanosine (m7G) on tRNAs is a heat-responding modification that is critical for yeast survival under high temperature, while its function and mechanism in HCC recurrence after IRFA are unknown. Here, we found that IRFA significantly up-regulates the level of m7G tRNA modification and its methyltransferase complex components METTL1 and WDR4 in multiple systems including HCC patient-derived xenograft (PDX) mouse, HCC tissues of patients, sublethal-heat-treated models of HCC cell lines and organoids. Functionally, gain- or loss-of function assays showed that METTL1 mediated m7G tRNA modification promotes HCC metastasis under sublethal heat exposure both in vitro and in vivo. Mechanistically, we found that METTL1 and m7G tRNA modification enhance the translation of SLUG and SNAIL in a codon frequency dependent manner under sublethal heat exposure. Overexpression of SLUG and SNAIL rescued the malignant potency of METTL1 knockdown HCC cells after sublethal heat stress. Our study uncovers the important physiological functions of m7G tRNA modification in heat stress responses and HCC recurrence after IRFA and suggests that targeting METTL1-m7G-SLUG and SNAIL axis could be a promising strategy to prevent HCC metastasis after radiofrequency heat ablation treatment.
Project description:The human genome encodes tens of thousands circular RNAs (circRNAs) with mostly unknown functions. Circular RNAs requires internal ribosome entry sites (IRES) if they are to undergo translation without 5’ cap. Here, we develop a high-throughput screen to systematically discover RNA sequences that can direct circRNA translation in human cells. We identify over 17,000 endogenous and synthetic sequences as candidate circRNA IRES. 18S rRNA complementarity and a structured RNA element positioned on the IRES are important for driving circRNA translation. Ribosome profiling and peptidomic analyses show extensive IRES-ribosome association, hundreds of circRNA-encoded proteins with tissue -specific distribution, and antigen presentation. We find that circFGFR1p, a protein encoded by circFGFR1 that is down regulated in cancer, functions as a negative regulator of FGFR1 oncoprotein to suppress cell growth during stress. Systematic identification of circRNA IRES elements may provide important links among circRNA regulation, biological function, and disease.
Project description:Translation initiation of eukaryotic mRNAs mostly occurs by the cap-dependent ribosome scanning mechanism. However, certain mRNAs are translated by ribosome assembly at internal ribosome entry sites (IRES), a mechanism that allows the synthesis of certain proteins when cap-dependent translation is inhibited by cellular stress. Whether IRES-mediated translation occurs in stressed human endothelial cells (EC) is unknown. We performed whole genome microarray analysis of polyribosomal mRNA (43,203 sequences) from virus-infected EC to identify IRES-containing mRNAs.
Project description:The tRNA N7-methylguanosine (m7G) modification is not essential for yeast growth, but in mammals mis-regulations of tRNA m7G modification cause stem cell defect and developmental disorders. Here we found that tRNA m7G methyltransferase complex components METTL1 and WDR4 are elevated in lung cancer tissues and associated with poor lung cancer prognosis. Functionally, depletion of METTL1 or WDR4 suppresses proliferation, migration, and invasion of lung cancer cells. In addition, forced expression of METTL1 or WDR4 promotes lung cancer progression depending on the tRNA m7G methyltransferase activity. Mechanistically, METTL1 knockdown leads to reduced tRNA m7G modification and decreased expression of m7G-modified tRNAs. Depletion of METTL1 selectively reduces the translation of a subset of oncogenic transcripts, including the genes related to cell proliferation in a m7G related codon dependent manner. Our study uncovered a new layer of translation regulation mechanism mediated by tRNA m7G modification, provided strong evidence to support the important physiological function of mis-regulated tRNA modification in cancer, and suggested that targeting METTL1 could be a promising strategy for lung cancer treatment.
Project description:The tRNA N7-methylguanosine (m7G) modification is not essential for yeast growth, but in mammals mis-regulations of tRNA m7G modification cause stem cell defect and developmental disorders. Here we found that tRNA m7G methyltransferase complex components METTL1 and WDR4 are elevated in lung cancer tissues and associated with poor lung cancer prognosis. Functionally, depletion of METTL1 or WDR4 suppresses proliferation, migration, and invasion of lung cancer cells. In addition, forced expression of METTL1 or WDR4 promotes lung cancer progression depending on the tRNA m7G methyltransferase activity. Mechanistically, METTL1 knockdown leads to reduced tRNA m7G modification and decreased expression of m7G-modified tRNAs. Depletion of METTL1 selectively reduces the translation of a subset of oncogenic transcripts, including the genes related to cell proliferation in a m7G related codon dependent manner. Our study uncovered a new layer of translation regulation mechanism mediated by tRNA m7G modification, provided strong evidence to support the important physiological function of mis-regulated tRNA modification in cancer, and suggested that targeting METTL1 could be a promising strategy for lung cancer treatment.
Project description:N7-methylguanosine (m7G) modification is one of the most prevalent tRNA modifications in human. The precise function and molecular mechanism of m7G tRNA modification in regulation of cancer remain poorly understood. Here we showed that m7G tRNA modification, METTL1 and WDR4 are elevated in hepatocellular carcinoma (HCC) tissues and associated with HCC patient prognosis. Functionally, silencing METTL1 or WDR4 inhibits HCC cell proliferation, migration and invasion, while forced expression of wild type METTL1 but not its catalytic dead mutant promotes HCC progression. Knockdown of METTL1 reduces m7G tRNA modification and decreases m7G modified tRNA expression. Mechanistically, METTL1 depletion selectively decreases the mRNA translation of a subset of oncogenic genes, especially cell cycle and EGFR pathway genes, in m7G-related codon dependent manner. Moreover, in vivo studies using Mettl1 knock-in and knockout mice reveal a critical function of Mettl1 mediated m7G tRNA modifications in promoting hepatocarcinogenesis in the hydrodynamics transfection HCC model. Our work uncovers the critical functions of tRNA m7G modification in regulating cancer mRNA translation and promoting hepatocarcinogenesis, thus provides new insights into role of the mis-regulated tRNA modifications in cancers.