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. Size selected RNASeq of 3 human embryonic kidney cell (HEK293) samples. 1 control and 2 samples exposed to 100 μg/ml ethyl methanesulfonate for 24 hrs.
Project description:<p>High throughput RNA Sequencing has revealed that the human genome is widely transcribed. However, the extent of natural antisense transcription, the molecular mechanisms by which natural antisense transcripts (NATs) might affect their cognate sense genes, and the role of NATs in cancer are less well understood. Here, we use strand-specific paired-end RNA sequencing (ssRNASeq) on a cohort of 376 cancer patients covering 9 tissue types to comprehensively characterize the landscape of antisense expression. Our results reveal that greater than 60% of annotated transcripts have measureable antisense expression and the expression of sense and antisense transcript pairs is in general positively correlated. Furthermore, by studying the expression of sense/antisense pairs across tissues we identify lineage-specific, ubiquitous and cancer-specific antisense loci. Our results raise the possibility that NATs participate in the regulation of well-known tumor suppressors and oncogenes. Finally, this study provides a catalogue of cancer related genes with significant antisense transcription (oncoNAT). This resource will allow researchers to investigate the molecular mechanisms of sense/antisense regulation and further advance our understanding of their role in cancer.</p>
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.
Project description:We have previously reported that elevated fibroblast growth factor-2 (FGF-2) expression is associated with tumor recurrence and reduced survival after surgical resection of esophageal cancer, and that these risks are reduced in tumors co-expressing an endogenous antisense (FGF-AS) RNA. In the present study we examined the role of the endogenous FGF-AS transcript in the regulation of FGF-2 expression in the human lung adenocarcinoma cell line, Seg-1. FGF-2 and FGF-AS were temporally and spatially co-localized in the cytoplasm of individual cells, and knock-down of either FGF-2 or FGF-AS by target specific siRNAs resulted in dose-dependent up-regulation of the complementary transcript and its encoded protein product. Using a luciferase reporter system we show that these effects are mediated by interaction of the endogenous antisense RNA with the 3âUTR of the FGF-2 mRNA. Deletion mapping identified a 392 nt sequence in the 5823 nucleotide FGF-2 untranslated tail which is targeted by FGF-AS. siRNA-mediated knockdown of either FGF-AS or FGF-2 significantly increased the stability of the complementary partner mRNA, demonstrating that these mRNAs are mutually regulatory. Knockdown of FGF-AS also resulted in reduced expression of argonaute-2 (AGO-2) and a number of other elements of the endogenous microRNA/RNAi pathways. Conversely, siRNA-mediated knockdown of AGO-2 significantly increased the stability of the FGF-2 mRNA transcript, and the steady-state levels of both FGF-2 mRNA and protein, suggesting a role for AGO-2 in the regulation of FGF-2 expression. Experiment Overall Design: Gene expression in Seg-1 cells transfected with FGF-AS siRNA was compared to gene expression in Seg-1 cells transfected with negative control siRNA using Affymetrix Human Genome U133 Plus 2.0 arrays
Project description:Arabidopsis thaliana (Arabidopsis) encodes five DOUBLE-STRANDED RNA BINDING (DRB) proteins, DRB1 to DRB5, that predominantly act as non-catalytic cofactors for DICER-LIKE (DCL) proteins in the double-stranded RNA (dsRNA) processing stages of small RNA (sRNA) production pathways. In the nucleus, DRB1 is required for microRNA (miRNAs) processing from imperfectly dsRNA precursors by DCL1. Similarly, DRB4 is required by DCL4 for small-interfering RNAs (siRNAs) production from endogenous or exogenous perfectly dsRNA templates. DRB2 has been recently demonstrated to be required for miRNA and siRNA production in developmentally-important tissues of Arabidopsis while the requirement of either DRB3 or DRB5 in sRNA production remains unclear. Here, we analyse in parallel, the contribution of all five DRB protein family members to the global sRNA landscape of Arabidopsis floral tissues. In depth bioinformatic analysis of sRNA sequencing datasets generated from floral tissues of DRB knockout mutant (drb) plant lines, drb1, drb2, drb4, drb12, drb14, drb24, and drb35 and their comparison to the floral sRNA profile of wild-type Arabidopsis, has enabled confident assignment of the requirement of DRB1, DRB2 and DRB4 for the production of specific miRNA and siRNA subclasses in this tissue. Our analyses have additionally identified novel and/or expanded roles for DRB2 in miRNA, trans-acting siRNAs (tasiRNAs) and natural antisense transcript siRNAs (natsiRNAs) production.
Project description:Multiple sclerosis (MS) is an inflammatory disease of the central nervous system and is generally considered to be autoimmune in nature. We previously demonstrated that the transcription factor Sp3 is significantly down-regulated in immune cells from MS patients. The potential role of Sp3 down-regulation in MS pathogenesis is not well understood. The function of endogenous Sp3 was assessed in vitro after siRNA-mediated knockdown of its transcript in Jurkat cells. Sp3 protein levels were reduced an average of 70%. ELISA studies demonstrated decreased endogenous production of IL-10 and TGFβ1 and increased endogenous production of TNFα (p<0.05 in all assays). Subsequent microarray analysis demonstrated significantly altered expression of 36 genes (p<0.001 for each gene) compared with control samples. Analysis showed differential expression (p<0.005) of 8 gene pathways. Many of the genes and pathways that were regulated by Sp3 are involved in immune function, specifically with regard to apoptosis, cell-to-cell adhesion, integrin signaling, T-cell differentiation, and cytokine production. This study identifies mechanisms by which Sp3 may regulate immune function and suggests a basis for its potential contribution to MS disease pathogenesis. Experiment Overall Design: Two Sp3 siRNA knockdown groups (siRNA Sp3 #2: n=3, and #6: n=3) were clustered together into the Treated condition, and the two control groups (siRNA for GAPDH: n=3, and Non-transfected cells: n=3)were assembled to constitute the Control condition. Thus a total of 12 arrays (6 Controls and 6 treated) were used in this experiment.