Genomic Helicase-SELEX
Ontology highlight
ABSTRACT:
PROVIDER: PRJEB50170 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| ERR8958114_1.fastq.gz | Fastqsanger.gz | |||
| ERR8958114_2.fastq.gz | Fastqsanger.gz | |||
| ERR8958116_1.fastq.gz | Fastqsanger.gz | |||
| ERR8958116_2.fastq.gz | Fastqsanger.gz |
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Project description:Ribonucleases (RNases) are central actors in post-transcriptional regulation, a major level of regulation of gene expression in all cells. This control plays an important role in the bacterial pathogen Helicobacter pylori, although only the function of RNase J was characterized so far. Here, we studied the RNase R enzyme from H. pylori, a 3’-5’ exoribonuclease whose ortholog in Escherichia coli was reported to display, in addition, helicase activity and to be able to hydrolyze RNA substrates with double stranded structures. We observed that HpRNase R protein does not carry the domains responsible for helicase activity in E. coli and accordingly that the purified protein is unable to degrade in vitro RNA molecules with secondary structures. The RNase R helicase domain loss is widespread among the Campylobacterota and occurred gradually during their evolution. Furthermore, an in vivo interaction between HpRNase R and RhpA, the sole DEAD-box RNA helicase of H. pylori, was discovered. Phylogenomics suggests that this interaction might occur in other bacteria of the phylum Campylobacterota. Purified RhpA facilitates the degradation of double stranded RNA substrates by HpRNase R, showing that this complex is functional. HpRNase R has a minor role of in 5S rRNA maturation and, as shown by RNA-Seq, few targets in H. pylori all of them being included in the RhpA regulon. In conclusion, we describe a new type of RNase R that lacks some of the features that were considered as hallmarks of RNase R proteins, but that has co-opted another RNA helicase, which we hypothesize helps it accomplish some of its functions in vivo.
2021-06-19 | E-MTAB-10045 | biostudies-arrayexpress
Project description:Years after the discovery that Dicer is a key enzyme in gene-silencing, the role of its helicase domain remains enigmatic. Here we show that this domain is critical for accumulation of certain endogenous small interfering RNAs (endo-siRNAs) in C. elegans. The domain is required for the production of the direct products of Dicer, or primary endo-siRNAs, and consequently, affects levels of downstream intermediates, the secondary endo-siRNAs. Consistent with the role of endo-siRNAs in silencing, their loss correlates with an increase in cognate mRNA levels. We find that the helicase domain of Dicer is not required for microRNA (miRNA) processing, or RNA interference following exposure to exogenous double-stranded RNA. Comparisons of wildtype and helicase-defective strains using deep-sequencing analyses show that the helicase domain is required by a subset of annotated endo-siRNAs, in particular, those associated with the slightly longer 26 nucleotide small RNA species containing a 5M-bM-^@M-^Y guanosine. We reintroduced either wildtype Dicer, or Dicer harboring a mutation (K39A) in it's helicase domain, into dcr-1(ok247) mutant worms via transgene rescue. We then used high-throughput sequencing to compare levels of small RNAs present in each of these strains.
2010-04-01 | E-GEOD-20336 | biostudies-arrayexpress
Project description:Transcription termination by Rho is essential for viability in various bacteria, including some major pathogens. Since Rho acts by targeting nascent RNAs that are not simultaneously translated, it also regulates antisense transcription. Here we show that RNase H-deficient mutants of Escherichia coli exhibit heightened sensitivity to the Rho inhibitor bicyclomycin, and that Rho deficiency provokes increased formation of RNA-DNA hybrids (R-loops) which is ameliorated by expression of the phage T4-derived R-loop helicase UvsW. We also provide evidence that in Rho-deficient cells, R-loop formation blocks subsequent rounds of antisense transcription at more than 500 chromosomal loci. Hence these antisense transcripts, which can extend beyond 10 kb in their length, are only detected when Rho function is absent or compromised and the UvsW helicase is concurrently expressed. Thus the potential for antisense transcription in bacteria is much greater than hitherto recognized; and the cells are able to retain viablity even when nearly one-quarter of their total non-rRNA abundance is accounted for by antisense transcripts, provided that R-loop formation from them is curtailed.
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Project description:Years after the discovery that Dicer is a key enzyme in gene-silencing, the role of its helicase domain remains enigmatic. Here we show that this domain is critical for accumulation of certain endogenous small interfering RNAs (endo-siRNAs) in C. elegans. The domain is required for the production of the direct products of Dicer, or primary endo-siRNAs, and consequently, affects levels of downstream intermediates, the secondary endo-siRNAs. Consistent with the role of endo-siRNAs in silencing, their loss correlates with an increase in cognate mRNA levels. We find that the helicase domain of Dicer is not required for microRNA (miRNA) processing, or RNA interference following exposure to exogenous double-stranded RNA. Comparisons of wildtype and helicase-defective strains using deep-sequencing analyses show that the helicase domain is required by a subset of annotated endo-siRNAs, in particular, those associated with the slightly longer 26 nucleotide small RNA species containing a 5’ guanosine.
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Project description:BackgroundSELEX is a well established in vitro selection tool to analyze the structure of ligand-binding nucleic acid sequences called aptamers. Genomic SELEX transforms SELEX into a tool to discover novel, genomically encoded RNA or DNA sequences binding a ligand of interest, called genomic aptamers. Concerns have been raised regarding requirements imposed on RNA sequences undergoing SELEX selection.Methodology/principal findingsTo evaluate SELEX and assess the extent of these effects, we designed and performed a Neutral SELEX experiment omitting the selection step, such that the sequences are under the sole selective pressure of SELEX's amplification steps. Using high-throughput sequencing, we obtained thousands of full-length sequences from the initial genomic library and the pools after each of the 10 rounds of Neutral SELEX. We compared these to sequences obtained from a Genomic SELEX experiment deriving from the same initial library, but screening for RNAs binding with high affinity to the E. coli regulator protein Hfq. With each round of Neutral SELEX, sequences became less stable and changed in nucleotide content, but no sequences were enriched. In contrast, we detected substantial enrichment in the Hfq-selected set with enriched sequences having structural stability similar to the neutral sequences but with significantly different nucleotide selection.Conclusions/significanceOur data indicate that positive selection in SELEX acts independently of the neutral selective requirements imposed on the sequences. We conclude that Genomic SELEX, when combined with high-throughput sequencing of positively and neutrally selected pools, as well as the gnomic library, is a powerful method to identify genomic aptamers.
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