Project description:The RNA editing enzyme ADAR chemically modifies adenosine (A) to inosine (I), which is interpreted by the ribosome as a guanosine. Here we assess cotranscriptional A-to-I editing in Drosophila, by isolating nascent RNA from adult fly heads and subjecting samples to high-throughput sequencing. There are a large number of edited sites within nascent exons. Nascent RNA from an ADAR null mutant strain was also sequenced, indicating that almost all A-to-I events require ADAR. Moreover, mRNA editing levels correlate with editing levels within the cognate nascent RNA sequence, indicating that the extent of editing is set cotranscriptionally. Surprisingly, the nascent data also identify an excess of intronic over exonic editing sites. These intronic sites occur preferentially within introns that are poorly spliced cotranscriptionally, suggesting a link between editing and splicing. We conclude that ADAR-mediated editing is more widespread than previously indicated and largely occurs cotranscriptionally.
Project description:To determine the prevalence of cotranscriptional splicing in Drosophila, we sequenced nascent RNA transcripts from Drosophila S2 cells as well as from Drosophila heads. 87% of introns assayed manifest more than 50% cotranscriptional splicing. The remaining 13% are cotranscriptionally spliced poorly, or slowly, with ~3% being almost completely retained in nascent pre-mRNA. Although individual introns showed slight but statistically significant differences in splicing efficiency, similar global levels of splicing were seen from both sources. Importantly, introns with low cotranscriptional splicing efficiencies are present in the same primary transcript with efficiently spliced introns, indicating that splicing is intron-specific. The analysis also indicates that cotranscriptional splicing is less efficient for first introns, longer introns and introns annotated as alternative. FinallyFinally, S2 cells expressing the slow RpII215C4 mutant manifest substantially less intron retention than wild-type S2 cells. Examination of Total pA and Nascent RNA from 2 different cell populations and isolated fly heads.
Project description:The RNA editing enzyme ADAR chemically modifies adenosine (A) to inosine (I), which is interpreted by the ribosome as a guanosine. Here we assess cotranscriptional A-to-I editing in Drosophila, by isolating nascent RNA from adult fly heads and subjecting samples to high-throughput sequencing. There are a large number of edited sites within nascent exons. Nascent RNA from an ADAR null mutant strain was also sequenced, indicating that almost all A-to-I events require ADAR. Moreover, mRNA editing levels correlate with editing levels within the cognate nascent RNA sequence, indicating that the extent of editing is set cotranscriptionally. Surprisingly, the nascent data also identify an excess of intronic over exonic editing sites. These intronic sites occur preferentially within introns that are poorly spliced cotranscriptionally, suggesting a link between editing and splicing. We conclude that ADAR-mediated editing is more widespread than previously indicated and largely occurs cotranscriptionally. GSM914095: Fly genomic DNA sequencing. Sequenced on the Illumina GA II. GSM914102-GSM914113: Fly head nascent RNA profiles over 6 time points of a 12hr light:dark cycle in duplicate; sequenced on the Illumina GA II. GSM914114-GSM914119: Fly head nascent RNA profiles of yw, FM7, ADAR0 males in duplicate; sequenced on the HiSeq2000. GSM915213-GSM915214: Fly head mRNA profiles over 2 time points of a 12hr light:dark cycle; sequenced on the Illumina GA II. GSM915215-GSM915220: Fly head mRNA profiles over 6 time points of a 12hr light:dark cycle; paired-end sequenced on the Illumina GA II. GSM915221-GSM91526: Fly head mRNA profiles over 6 time points of a 12hr light:dark cycle; sequenced on the Illumina GA II.
Project description:To determine the prevalence of cotranscriptional splicing in Drosophila, we sequenced nascent RNA transcripts from Drosophila S2 cells as well as from Drosophila heads. 87% of introns assayed manifest more than 50% cotranscriptional splicing. The remaining 13% are cotranscriptionally spliced poorly, or slowly, with ~3% being almost completely retained in nascent pre-mRNA. Although individual introns showed slight but statistically significant differences in splicing efficiency, similar global levels of splicing were seen from both sources. Importantly, introns with low cotranscriptional splicing efficiencies are present in the same primary transcript with efficiently spliced introns, indicating that splicing is intron-specific. The analysis also indicates that cotranscriptional splicing is less efficient for first introns, longer introns and introns annotated as alternative. FinallyFinally, S2 cells expressing the slow RpII215C4 mutant manifest substantially less intron retention than wild-type S2 cells.
Project description:Purpose: Validation of Drosophila A-to-I editing sites Methods: We collected heads of 5 day old male dAdar-/- mutant (y, Adar5G1, w)26 and wild type (w1118) flies. Poly(A)+ RNA was used to prepare RNA-seq libraries which were subsequently sequenced single-end by an Illumina GAII Results:We builded a framework to identify RNA editing events using RNA-seq data alone in Drosophila. To validate whether the identified A-to-G sites were bona fide A-to-I editing events, we performed RNA-seq for the D.melanogaster wild-type strain (w1118) and for the Adar5G1 null mutant that eliminates RNA editing. We found that our method achieved high accuracy; 98.2% of all A-to-G sites showed only adenosine in the Adar5G1 sample Conclusions: We anticipate that our method will be very effective in the future to identify RNA editing events in different species. mRNA profiles of heads of 5 day old male dAdar-/- mutant (y, Adar5G1, w)26 and wild type (w1118) flies
Project description:We applied microfluidic multiplex PCR and deep sequencing (mmPCR-seq) to quantify RNA editing levels at targeted sites in Drosophila melanogaster, Drosophila sechellia and the species-specific alleles of their F1 hybrids to understand the contribution of cis and trans regulatory factors to regulating RNA editing levels.
Project description:To identify TF binding motifs with position-dependent functions associated with transcription initiation, we performed csRNA-seq to map initiating transcripts in Drosophila melanogaster embryos. We started with cell culturing and csRNA-seq for data acquisition. This was followed by a csRNA-seq bioinformatics analysis comparing TSS with more vs. less nascent transcription.
Project description:Purpose: Validation of Drosophila A-to-I editing sites Methods: We collected heads of 5 day old male dAdar-/- mutant (y, Adar5G1, w)26 and wild type (w1118) flies. Poly(A)+ RNA was used to prepare RNA-seq libraries which were subsequently sequenced single-end by an Illumina GAII Results:We builded a framework to identify RNA editing events using RNA-seq data alone in Drosophila. To validate whether the identified A-to-G sites were bona fide A-to-I editing events, we performed RNA-seq for the D.melanogaster wild-type strain (w1118) and for the Adar5G1 null mutant that eliminates RNA editing. We found that our method achieved high accuracy; 98.2% of all A-to-G sites showed only adenosine in the Adar5G1 sample Conclusions: We anticipate that our method will be very effective in the future to identify RNA editing events in different species.