Project description:Using CLIP-seq, hm5C RIP-seq, and small RNA-seq, we show that TET2 binds to tRNAs in mouse embryonic stem cells at sites enriched for hm5C. Loss of TET2 causes decreased hm5C on tRNAs and abrogation of all TET activity led to changes in 5' and 3' tRNA fragments.
Project description:Argonaute/Piwi proteins associate with small RNAs that typically provide sequence specificity for RNP function in gene and genome regulation. Here we show that Twi12, a Tetrahymena Piwi protein essential for growth, is loaded with mature tRNA fragments. The tightly bound ~18-22 nt tRNA 3M-bM-^@M-^Y fragments are biochemically distinct from the tRNA halves produced transiently in response to stress. Notably, the end positions of Twi12-bound tRNA 3' fragments precisely match RNAs detected in total small RNA of mouse embryonic stem cells and human cancer cells. Our studies demonstrate unanticipated evolutionary conservation of mature tRNA processing to tRNA-fragment small RNAs. Two libraries are analyzed here: sRNAs associated with slightly overexpressed ZZ-tagged Twi12 purified under native conditions (size range 15-34nt), and those associated after formaldehyde crosslinking (15-22nt).
Project description:Argonaute/Piwi proteins associate with small RNAs that typically provide sequence specificity for RNP function in gene and genome regulation. Here we show that Twi12, a Tetrahymena Piwi protein essential for growth, is loaded with mature tRNA fragments. The tightly bound ~18-22 nt tRNA 3’ fragments are biochemically distinct from the tRNA halves produced transiently in response to stress. Notably, the end positions of Twi12-bound tRNA 3' fragments precisely match RNAs detected in total small RNA of mouse embryonic stem cells and human cancer cells. Our studies demonstrate unanticipated evolutionary conservation of mature tRNA processing to tRNA-fragment small RNAs.
Project description:We report the identification and quantification of Watson-Crick modifications in tRNA and rRNA through the use of high throughput sequencing. We apply the recently published DM-tRNA-Seq method to generate demethylase treated and untreated 293T samples, and using computational methods we are able to flag sites using a modification index. This index allows us to generate site-resolved information about modification that we can use to identify and quantify Watson-Crick face modifications in tRNA and rRNA. With the demethylase treated samples, we are able to validate numerous nucleotide modifications from demethylase substrates, and the absence of demethylase action also serves to aid in identification. We find numerous novel modification sites in tRNA as well as striking comparisons between tissues cultures lines. Our study reports a comprehensive analysis of the tRNA modification landscape by identifying sites of modification as well as quantifying modification levels.
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.
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:Post-transcriptional modifications are important for transfer RNAs (tRNAs) to be efficient and accurate in translation on the ribosome. The m1G37 modification on a subset of tRNAs in bacteria are generated by a conserved methyltransferase TrmD and is essential for bacterial growth. Previous studies showed that m1G37 has an important role in preventing translational frameshifting and also that this modification is coupled with aminoacylation of tRNAs for proline. Here we performed suppressor screening to isolate a mutant E. coli cell that lacks TrmD but is viable, and the whole-genome sequencing revealed several mutations on prolyl-tRNA synthetase (ProRS) gene conferring cell viability in the absence of TrmD. Biochemical assays confirmed uncoupling of m1G37 modification and aminoacylation, and cell-based assays uncovered the critical role of m1G37 in supporting Wobble decoding.
Project description:Loss of CLP1 activity results in the accumulation of novel sets of small RNA fragments derived from aberrant processing of tyrosine pre-tRNA. Such tRNA fragments sensitize cells to oxidative stress-induced p53 activation and p53-dependent cell death. 2 samples, Wt and Clp1(k/k), no replicates