Dataset Information

Uncovering deeply conserved motif combinations in rapidly evolving noncoding sequences

ABSTRACT: Here we focus on identifying conserved elements that are required for Chaserr function, a lncRNA that we recently characterized as being essential for mouse viability (https://doi.org/10.1038/s41467-019-13075-8). Chaserr is highly conserved in different species, and is located in close proximity (<2kb) to the transcription start site of CHD2. It acts in concert with the CHD2 protein to maintain proper Chd2 expression levels. Using the LncLOOM framework we identified AUGG enriched conserved elements which are located in the last exon of mouse Chaserr. In order to identify proteins that potentially bind to these conserved regions, we used in vitro transcription to generate the following biotinylated RNAs; along with their antisense controls: 1) The WT sequence, containing the first 322 nt of the last exon of Chaserr (bases 764–1086 of the NR_037601 isoform). An antisense control fragment was also prepared, labelled as AWT 2) The mutant conserved (MC) sequence, that contained AUGG→UACC mutations in four conserved motifs that were found using LncLOOM. An antisense control fragment was also prepared, labelled as AMC 3) The muatant all (MA) sequence in which all seven of the AUGG sites in the last exon were mutated to UACC. An antisense control fragment was also prepared, labelled as AMA 4) We also included a No Probe Control, which did not contain an RNA fragment. The fragments were incubated with N2a cell lysates followed by RNA-pulldown and Mass Spec analysis. The experiment was performed in triplicate. A total of 938 proteins were found to associate with the WT sequence: 74 of these were enriched ≥3-fold compared to the antisense sequence.We identified 9 proteins that had ≥2-fold higher recovery when using the WT sequence compared to both mutants. Included in these proteins was DHX36, which showed the highest enrichment compared to the mutated sequences. We validated the association of DHX36 with Chaserr through RNA immunoprecipitation experiments.

INSTRUMENT(S): Q Exactive HF

ORGANISM(S): Mus Musculus (mouse)

SUBMITTER: Caroline Ross

LAB HEAD: Igor Ulitsky

PROVIDER: PXD023093 | Pride | 2021-01-18

REPOSITORIES: Pride

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Uncovering deeply conserved motif combinations in rapidly evolving noncoding sequences.

Ross Caroline Jane CJ Rom Aviv A Spinrad Amit A Gelbard-Solodkin Dikla D Degani Neta N Ulitsky Igor I

Genome biology 20210111 1

<h4>Background</h4>Animal genomes contain thousands of long noncoding RNA (lncRNA) genes, a growing subset of which are thought to be functionally important. This functionality is often mediated by short sequence elements scattered throughout the RNA sequence that correspond to binding sites for small RNAs and RNA binding proteins. Throughout vertebrate evolution, the sequences of lncRNA genes changed extensively, so that it is often impossible to obtain significant alignments between sequences ...[more]

PMID: 33430943

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Project description:Background: Eukaryotic cells express a complex layer of noncoding RNAs. An intriguing family of regulatory RNAs includes transcripts from the opposite strand of protein coding genes, so called natural antisense transcripts (NATs). Here, we test the hypothesis that antisense transcription triggers RNA interference and gives rise to endogenous short RNAs (endo-siRNAs). Methods/Results: We used cloned human embryonic kidney cells (HEK293) followed by short RNAseq to investigate the small genic RNA transcriptome. 378 genes gave rise to short RNA reads that mapped to exons of RefSeq genes. The length profile of short RNAs showed a broad peak of 20-24 nucleotides, indicative of endo-siRNAs. Collapsed reads mapped predominantly to the first and the last exon of genes (74%). RNAs reads were intersected with sequences occupied by RNAPolII or bound to Argonaute (AGO1 by crosslinking, ligation, and sequencing of hybrids, CLASH). In the first exon, 94% of the reads correlated with PolII occupancy with an average density of 130 (relative units); this decreased to 65%/20 in middle exons and 54%/12 in the last exon. CLASH reads mapping to multi-exon genes showed little distribution bias with an average of about 5 CLASH reads overlapping with 60% of the endo-siRNA reads. However, endo-siRNAs (21-25 nt) intersecting with CLASH reads were enriched at the 5'end and decreased towards the 3'end. We then investigated the 378 genes with particular focus on features indicative for short RNA production; however, found that endo-siRNA numbers did not correlate with gene structures that favor convergent transcription. In contrast, our gene set was found notably over-represented in the NATsDB sense/antisense group as compared to non-overlapping and non-bidirectional groups. Moreover, read counts showed no correlation with the steady-state levels of the related mRNAs and the pattern of endo-siRNAs proved reproducible after an induced mutagenic insult. Conclusions: Our results suggest that antisense transcripts contribute to low levels of endo-siRNAs in fully differentiated human cells. A characteristic endo-siRNA footprint is being produced at sites of RNAPolII transcription which is also related to AGO1. This endo-siRNA signature represents an intriguing finding and its reproducibility suggests that the production of endo-siRNAs is a regulated process with potential homoeostatic impact.

Dataset Information

Uncovering deeply conserved motif combinations in rapidly evolving noncoding sequences

Publications

Uncovering deeply conserved motif combinations in rapidly evolving noncoding sequences.

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