Ribosome profiling performed in Mycobacterium smegmatis MC2 155wild type and ORF MSMEG_0945 MSMEG_1916 mutants
Ontology highlight
ABSTRACT:
INSTRUMENT(S): NextSeq 500
ORGANISM(S): Mycolicibacterium smegmatis MC2 155
SUBMITTER: Anne Stringer
PROVIDER: E-MTAB-12798 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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Project description:We measured global RNA levels using RNA-seq in Mycobacterium smegmatis MC2 155 wild-type cells versus cells with deletions of genes encoding small ORFs MSMEG_0945 and MSMEG_1916.
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Project description:Open reading frame (ORF) boundaries in bacterial genomes have largely been drawn by gene prediction algorithms. However, these algorithms often fail to predict ORFs with non-canonical features, including those that are short, overlapping, or lack 5’ UTRs. Recent developments in genome-scale mapping of translation have facilitated the empirical identification of open reading frames (ORFs). Here, we use ribosome profiling approaches to map initiating and elongating ribosomes in Mycobacterium tuberculosis. Thus, we identify over 1,000 novel ORFs, revealing that much of the M. tuberculosis genome encodes proteins in overlapping reading frames, and/or on both strands. Most of the novel ORFs are short (sORFs), impeding their identification by traditional methods. The strong codon bias that characterizes annotated mycobacterial ORFs is not evident in the aggregate novel sORFs, and hence most are unlikely to encode functional proteins. Thus, our data suggest that bacterial transcriptomes are subject to pervasive translation that occurs as a result of the relatively low specificity requirements of initiating ribosomes. We speculate that the inefficiency of expressing spurious sORFs may be offset by positive contributions to M. tuberculosis biology through cis and trans regulatory activities of a small subset.
2019-06-20 | E-MTAB-8039 | biostudies-arrayexpress
Project description:Here we adapt native elongating transcript sequencing (NET-seq) to develop transcription elongation factor associated nascent elongating transcript sequencing (TEF-seq). In this the RNA polymerase II (Pol2) transcription elongation complex (TEC) is immunoprecipitated via associated transcription elongation factors (TEFs). Sequencing from the 3' end of the Pol2-associated nascent transcript shows the position of the final incorporated nucleotide giving strand-specific, single nucleotide resolution maps of the level of TEF association with Pol2 during transcription.
2021-01-18 | E-MTAB-4568 | biostudies-arrayexpress
Project description:Poly(A) tails are critical for mRNA stability and translation. However, recent studies have challenged this view, showing that poly(A) tail length and translation efficiency are decoupled in non-embryonic cells. Using TAIL-seq and ribosome profiling, we investigate poly(A) tail dynamics and translational control in the somatic cell cycle. We find dramatic changes in poly(A) tail lengths of cell cycle regulatory genes like CDK1, TOP2A, and FBXO5, explaining their translational repression in M phase. We also find that poly(A) tail length is coupled to translation when the poly(A) tail is <20 nucleotides. However, as most genes have >20 nucleotide poly(A) tails, their translation is regulated mainly via poly(A) tail length-independent mechanisms during the cell cycle. Specifically, we find that terminal oligopyrimidine (TOP) tract-containing transcripts escape global translational suppression in M phase and are actively translated. Our quantitative and comprehensive data provide a revised view of translational control in the somatic cell cycle. HeLa cells were synchronized at S or M phase, and subject to RNA-seq, ribosome profiling and TAIL-seq analysis.
2016-04-04 | E-GEOD-79664 | biostudies-arrayexpress
Project description:MicroRNAs regulate gene expression through deadenylation, repression and mRNA decay. However, the contribution of each mechanism in non-steady-state situations remains unclear. We monitored the impact of miR-430 on ribosome occupancy of endogenous mRNAs in wild type and dicer mutants lacking mature miR-430. Our results indicate that miR-430 reduces the number of ribosomes on target mRNAs before causing mRNA decay. Translational repression occurs before complete deadenylation, and disrupting deadenylation using an internal poly(A) tail did not block target repression. Finally, we observe that ribosome density along the length of the target mRNA remains constant, suggesting that translational repression occurs by reducing the initiation rate rather than reducing elongation or causing ribosomal drop-off. In summary, our results show that miR-430 regulates translation initiation before inducing mRNA decay. Time course parallel ribosome profiling and input mRNA quantification in wildtype and MZdicer mutant embryos
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Project description:MicroRNAs (miRNAs) are endogenous ~22-nucleotide RNAs that mediate important gene-regulatory events by pairing to the mRNAs of protein-coding genes to direct their repression. Repression of these regulatory targets leads to decreased translational efficiency and/or decreased mRNA levels, but the relative contributions of these two outcomes have been largely unknown, particularly for endogenous targets expressed at low-to-moderate levels. Here, we use ribosome profiling to measure the overall effects on protein production and compare these to simultaneously measured effects on mRNA levels. For both ectopic and endogenous miRNA regulatory interactions, lowered mRNA levels account for most (≥84%) of the decreased protein production. These results show that changes in mRNA levels closely reflect the impact of miRNAs on gene expression and indicate that destabilization of target mRNAs is the predominant reason for reduced protein output. Examine ribosome footprints and mRNA abundance of HeLa cells transfected with miR-1 or miR-155, versus mock-transfected cells, at two different time points post-transfection. Supplementary processed data files linked below. mir155_summaryTable.txt: log2 fold changes (miR-155-transfected versus mock-transfected HeLa cells, 32hr). mir1_summaryTable.txt: log2 fold changes (miR-1-transfected versus mock-transfected HeLa cells, 32hr).
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2021-06-30 | E-MTAB-10695 | biostudies-arrayexpress
Project description:The aim of this experiment is to compare nucleases used in ribosome profiling using Drosophila melanogaster Kc167 cells and human U2OS osteosarcoma cells. Ribosome profiling was performed from nuclease digested samples using sucrose cushion centrifugation separated ribosomes.
2015-01-08 | E-MTAB-2421 | biostudies-arrayexpress
Project description:In mammals, double-stranded RNA (dsRNA) plays roles in sequence-specific RNA interference, sequence-independent interferon response, and RNA editing by adenosine deaminases. We have previously shown that long hairpin dsRNA expression in cultured cells does not activate the interferon response, it is poorly processed into siRNAs, and it is partially edited. Here, we demonstrate that dsRNA expressed from transiently transfected plasmids strongly inhibits expression of co-transfected reporter plasmids but not expression of endogenous genes or reporters stably integrated in the genome. The inhibition is concentration-dependent and independent of a cell type, transfection method, or dsRNA sequence. The inhibition occurs at the level of translation and is mediated by protein kinase R (PKR). PKR binds the expressed dsRNA, becomes phosphorylated and changes its distribution along polysome fractions. In conclusion, we demonstrate that expression from plasmids is selectively repressed if one of co transfected plasmids produces dsRNA. Our results highlight the importance of proper controls and careful interpretation of co-transfection experiments. HEK293 cells (human origin) were transiently transfected with hairpin dsRNA-expressing (MosIR) and control (pCag) plasmids.
2013-12-27 | E-GEOD-46959 | biostudies-arrayexpress
Project description:Transient plasmid transfection is common approach for studies in cultured mammalian cells. To examine behavior of transfected plasmids, we analyzed their transcriptional landscape by deep sequencing. We found that plasmids generate different levels of transcripts virtually everywhere. Spurious transcription may have undesirable effects as some co-transfected plasmids inhibited expression of luciferase reporters in a dose-dependent manner. In one case, we attributed this effect to kan/neo resistance cassette, which generated a unique population of edited sense and antisense small RNAs. The unexpected complexity of expression of transiently transfected plasmids highlights the importance of appropriate experimental controls. HEK293 cells (human origin) transiently transfected with 4 various plasmids
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