Nm-seq finds thousands of modified 2’-O-methylation sites in mRNA with base precision
Ontology highlight
ABSTRACT: Nm-seq maps 2'-O-methylation sites in human mRNA with base precision The ribose of rna nucleotides can be 2′-O-methylated (nm). despite advances in high-throughput detection, the inert chemical nature of nm still limits sensitivity and precludes mapping in mrna. We leveraged the differential reactivity of 2′-O-methylated and 2′-hydroxylated nucleosides to periodate oxidation to develop nm-seq, a sensitive method for transcriptome-wide mapping of nm with base precision. nm-seq uncovered thousands of nm sites in human mrna with features suggesting functional roles.
Project description:2’-O-methylation (Nm) is one of the most abundant RNA epigenetic modification and plays vital roles in the post-transcriptional regulation of gene expression. Current Nm mapping approaches are normally limited to highly abundant RNAs and have significant technical hurdles in mRNAs or relatively rare non-coding RNAs (ncRNAs). Here, we developed a new method for enriching Nm sites by using RNA exoribonuclease (M. genitalium RNase R, MgR) and periodate oxidation reactivity to eliminate 2’-hydroxylated (2’-OH) nucleosides, coupled with sequencing (Nm-REP-seq). We revealed several novel classes of Nm-containing ncRNAs as well as mRNAs in humans, mice, and drosophila. We found that some novel Nm sites are present at fixed positions in different tRNAs and are potential substrates of fibrillarin (FBL) methyltransferase mediated by snoRNAs. Importantly, we discovered, for the first time, that Nm located at the 3’-end of various types of ncRNAs and fragments derived from them. Our approach precisely redefines the genome-wide distribution of Nm and provides new technologies for functional studies of Nm-mediated gene regulation.
Project description:2’-O-methylation (Nm) is a prevalent post-transcriptional RNA modification present in many cellular RNAs and plays a critical role in modulating both the physical properties and regulation of eukaryotic RNAs. Studies of Nm modifications in RNA have long been hampered by a lack of effective mapping methods. Previously reported approaches can work well for detecting Nm modifications on abundant RNAs, but face challenges when applied to low-abundant RNAs, such as mRNA, lack stoichiometric information, and are challenged by issues of RNA sample degradation due to chemical treatment. Here, we present Nm-Mut-seq, a mutation signature-based Nm mapping method, which uses a custom reverse transcriptase (RT) that installs mutations at Am, Cm, and Gm-modified sites (Um is undetectable by this method). Our work provides a much-needed approach to detect Nm at base resolution in low abundant RNAs and to estimate the stoichiometry of each modified site transcriptome-wide.
Project description:Queuosine (Q) is a conserved tRNA modification at the wobble anticodon position of tRNAs that read the codons of amino acids Tyr, His, Asn, and Asp. Q-modification in tRNA plays important roles in the regulation of translation efficiency and fidelity. Queuosine tRNA modification is synthesized de novo in bacteria, whereas the substrate for Q-modification in tRNA in mammals is queuine, the catabolic product of the Q-base of gut bacteria. This gut microbiome dependent tRNA modification may play pivotal roles in translational regulation in different cellular contexts, but extensive studies of Q-modification biology are hindered by the lack of high throughput sequencing methods for its detection and quantitation. Here, we describe a periodate-treatment method of biological RNA samples that enables single base resolution profiling of Q-modification in tRNAs by Nextgen sequencing. Periodate oxidizes the Q-base, which results in specific deletion signatures in the RNA-seq data. Unexpectedly, we found that periodate-treatment also enables the detection of several 2-thio-modifications including τm5s2U, mcm5s2U, cmnm5s2U, and s2C by sequencing in human and E. coli tRNA. We term this method Periodate-dependent analysis of queuosine and thio modification sequencing (PAQS-seq). We assess Q- and 2-thio-modifications at the tRNA isodecoder level, and 2-thio modification changes in stress response. PAQS-seq should be widely applicable in the biological studies of Q- and 2-thio-modifications in mammalian and microbial tRNAs.
Project description:The goal of this study is to compare transcriptome-wide Nm-seq on the poly A+ RNA of wild-type Raw264.7 macrophages to transcriptome-wide Nm-seq on the poly A+ RNA of Raw264.7 macrophages after VSV infection . The Nm-seq profiles of wild-type Raw264.7 poly A+ RNA and VSV infected Raw264.7 poly A+ RNA were generated by deep sequencing using Illumina HiSeq4000 sequencer.
Project description:The goal of this study is to compare transcriptome-wide Nm-seq on the poly A+ RNA of wild-type Raw264.7 macrophages to transcriptome-wide Nm-seq on the poly A+ RNA of Fbl+/- Raw264.7 macrophages . The Nm-seq profiles were generated by deep sequencing using Illumina HiSeq4000 sequencer.
Project description:Hydroxylated polychlorinated biphenyls are the metabolites produced from polychlorinated biphenyls (PCBs) by drug-metabolizing enzyme cytochrome P450 1A1. These compounds are bound to transthyretin, a major plasma thyroid hormone-binding protein in amphibian tadpoles. The compounds-transthyretin complexes are transferred into the brain across the blood brain barrier in mammals. Thus these compounds are suspected to disrupt neural development in brain. We studied about the effects of hydroxylated PCBs on the thyroid system in brain using metamorphosing tadpoles of African clawed toad, Xenopus laevis. The metamorphosis assay revealed that these compounds had inhibitory effects on the thyroid hormone-induced metamorphosis. This in vivo assay was a powerful tool to detect thyroid-disrupting activities, because we were not able to detect the inhibitory effects of these compounds using thyroid hormone-responsive reporter gene assay in a cultured Xenopus cell line. A genome-wide gene expression analysis in brain following short-term exposure to these compounds demonstrated that the delay of metamorphosis and the morphological thyroid-disrupting changes could be caused partially by disruption of the thyroid hormone-induced gene expression by hydroxylated PCBs. Furthermore, we associated functional ontology terms with the transcripts whose expression were altered by thyroid hormone alone, or thyroid hormone and hydroxylated PCBs. We suggested that these approachs using a technique of bioinformatics revealed molecular mechanism of thyroid-disrupting activities in vivo. Thyroid hormones induce amphibian metamorphosis and alter a lot of thyroid hormone-responsive gene expression. We studied about the effects of hydroxylated PCBs on TH-induced gene expression. Premetamorphic tadpoles were treated with 500 nM hydroxylated PCBs in the presence of 1 nM thyroid hormone for 4 days. After exposure period total RNA was extracted from brain. Study included at least three replicate of each treatment.