Revealing nascent RNA processing dynamics with nano-COP
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ABSTRACT:
PROVIDER: PRJNA645078 | ENA |
REPOSITORIES: ENA
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Project description:During maturation, eukaryotic precursor RNAs undergo processing events including intron splicing, 3’-end cleavage, and polyadenylation. Here, we describe nanopore analysis of CO-transcriptional Processing (nano-COP), a method for probing the timing and patterns of RNA processing. An extension of native elongating transcript sequencing (NET-seq), which quantifies transcription genome-wide through short-read sequencing of nascent RNA 3’ ends, nano-COP uses long-read nascent RNA sequencing to observe global patterns of RNA processing. First, nascent RNA is stringently purified through a combination of 4-thiouridine metabolic labeling and cellular fractionation. In contrast to cDNA or short-read–based approaches relying on reverse transcription or amplification, the sample is sequenced directly through nanopores to reveal the native context of nascent RNA. nano-COP identifies both active transcription sites and splice isoforms of single RNA molecules during synthesis, providing insight into patterns of intron removal and the physical coupling between transcription and splicing. The nano-COP protocol yields data within 3 days.
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Project description:Human genes have numerous exons that are differentially spliced within pre-mRNA. Understanding how multiple splicing events are coordinated across nascent transcripts requires quantitative analyses of transient RNA processing events in living cells. We developed nanopore analysis of CO-transcriptional Processing (nano-COP), in which nascent RNAs are directly sequenced through nanopores, exposing the dynamics and patterns of RNA splicing without biases introduced by amplification. nano-COP showed that in both human and Drosophila cells, co-transcriptional splicing occurs after RNA polymerase II transcribes several kilobases of pre-mRNA, suggesting that metazoan splicing transpires distally from the transcription machinery. Inhibition of the branch site recognition complex SF3B globally abolished co-transcriptional splicing in both species. Our findings revealed that splicing order does not strictly follow the order of transcription and is influenced by cis-regulatory elements. In human cells, introns with delayed splicing frequently neighbor alternative exons and are associated with RNA-binding factors. Moreover, neighboring introns in human cells tend to be spliced concurrently, implying that splicing occurs cooperatively. Thus, nano-COP unveils the organizational complexity of metazoan RNA processing.
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Project description:Mammalian chromatin is the site of both RNA polymerase II (Pol II) transcription and coupled RNA processing. However, molecular details of such co-transcriptional mechanisms remain obscure, partly due to technical limitations in purifying authentic nascent transcripts. We present a new approach to purify and profile nascent RNA, called Polymerase Intact Nascent Transcript (POINT) technology. This three-pronged methodology maps nascent RNA 5’ends (POINT-5), establishes the kinetics of co-transcriptional splicing patterns (POINT-nano) and profiles whole transcription units (POINT-seq). In particular, we show by depletion of the nuclear exonuclease Xrn2 that this activity acts selectively on cleaved 5’P-RNA at polyadenylation sites. Furthermore, POINT-nano reveals that splicing occurs either immediately after splice site transcription or is delayed until Pol II transcribes downstream sequences. Finally, we connect RNA cleavage and splicing with either premature or full-length transcript termination. We anticipate that POINT technology will afford full dissection of the complexity of co-transcriptional RNA processing.
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Project description:We report that slow transcription by mutant RNA pol II caused accumulation of polyadenylated histone mRNAs that extend past the stem loop processing site. UV irradiation, which decelerates pol II elongation, also induced long poly(A)+ histone transcripts. Inhibition of 3’ processing by slow pol II correlates with failure to recruit SLBP to histone genes. Chemical probing of nascent RNA structure showed that the stem loop fails to fold in transcripts made by slow pol II, thereby explaining the absence of SLBP and failure to process 3’ ends. These results show that regulation of transcription speed can modulate pre-mRNA processing by changing nascent RNA structure, and suggest a mechanism by which alternative processing could be controlled
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Project description:POINT technology illuminates the processing of polymerase-associated intact nascent transcripts
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Project description:To address co-transcriptional pre-mRNA processing events, Saccharomyces nascent RNA was isolated by chromatin fractionation and analyzed on a genome-wide high density tiling microarray. Co-transcriptional splicing efficiencies were derived by determination of intronic relative to exonic sequence concentrations. Nascent RNA, mRNA and genomic DNA were isolated from wild-type Saccharomyces cells and analyzed on a genome-wide high-density tiling microarry (Saccharomyces Tiling 1.0R Array, Affymetrix). At least 3 independent biological replicates were analyzed (nascent RNA (nRNA): 3 replicates, mRNA: 3 replicates, genomic DNA (gDNA): 4 replicates).
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Project description:To deeply investigate the details of the nano-SiO2 effects, we examined the gene expression profile alterations after nano-SiO2 treatment in BMMCs. The difference analysis between the groups showed that 285 genes were significantly expressed after treatment with nano-SiO2. Compared with the blank group, both nano-SiO2 exposure and DNP-HSA stimulation increased the expression of genes related to the MAPK signaling pathway in mast cells to varying degrees.
2022-07-05 | GSE206630 | GEO
Project description:We have generated single-nucleotide resolution, nascent transcription profiles from HeLa cells by developing Native Elongation Transcript sequencing technology for mammalian chromatin (mNET-seq). Our extensive data sets provide a substantial resource to study mammalian nascent transcript profiles. We reveal unanticipated phosphorylation states for RNA polymerase II C-terminal domain (Pol II CTD) at both gene ends. We also observe that following 5’ splice site cleavage by the spliceosome, upstream exon transcripts are tethered to Pol II CTD phosphorylated on the serine 5 position (S5P) which is accumulated over downstream exons. We further show that depletion of termination factors substantially reduces Pol II pausing at gene ends leading to termination defects. Remarkably termination factors play an additional promoter role by restricting non-productive RNA synthesis and redistributing Pol II CTD S2P to promoters. These data demonstrate that CTD phosphorylation is more dynamic and variably distributed across mammalian transcription units than previously envisaged. To monitor nascent RNA within the mammalian Pol II complex, and its association with different CTD phosphorylation states, we employed mNET-seq methodology on HeLa cells, complemented with direct sequencing of chromatin-bound RNA (ChrRNA-seq). mNET-seq was preformed using the antibodies 8WG16, CMA602, CMA603 and CMA601, which are specific for unphosphorylated CTD, Ser2 phosphorylation, Ser5 phosphorylation and all CTD isoforms, respectively. In another experiment, to evaluate the effect of transcription termination factors in nascent RNA production by Pol II, mNET-seq and complemented with ChrRNA-seq was preformed on HeLa cells transfected with siRNA against PTBP1, CPSF73, CstF64+CstF64tau or Xrn2, and the gene profiles were compared with profiles from HeLa transfected with siRNA for Luciferase generated by the same protocol.
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Project description:The coupled activities of RNA polymerase and the spliceosome are responsible for the abundance and isoform composition of mRNA in human cells. However, the dynamics of these megadalton enzymatic complexes working in concert on endogenous genes have not been described. Here, we establish a quasi-genome-scale platform for observing synthesis and processing kinetics of single nascent RNA molecules in real time. We find that all observed genes show transcriptional bursting. We also observe large kinetic variation in intron removal for single introns in single cells which is inconsistent with deterministic splice site selection. Transcriptome-wide footprinting of the U2AF complex further reveals widespread splice site selection within introns. We propose and validate a unified theoretical model for transcription and splicing based on pervasive stochastic recursive splicing.
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