Transcription start site identification in Bacillus subtilis
ABSTRACT: Cappable-seq was used to map transcription start sites globally in wild type Bacillus subtilis. Total RNA was isolated from cells grown in LB media until exponential phase. RNA corresponding to transcription start sites was capped with a 5' biotin tag, which was used for enrichment via a pull down with streptavidin beads. Enriched RNA was converted to cDNA and then subjected to illumina sequencing.
Project description:Cappable-seq was used to map transcription start sites globally in wild type Bacillus subtilis. Total RNA was isolated from cells grown in LB media until exponential phase. RNA corresponding to transcription start sites was capped with a 5' biotin tag, which was used for enrichment via a pull down with streptavidin beads. Enriched RNA was converted to cDNA and then subjected to illumina sequencing.
Project description:BACKGROUND:The initiating nucleotide found at the 5' end of primary transcripts has a distinctive triphosphorylated end that distinguishes these transcripts from all other RNA species. Recognizing this distinction is key to deconvoluting the primary transcriptome from the plethora of processed transcripts that confound analysis of the transcriptome. The currently available methods do not use targeted enrichment for the 5'end of primary transcripts, but rather attempt to deplete non-targeted RNA. RESULTS:We developed a method, Cappable-seq, for directly enriching for the 5' end of primary transcripts and enabling determination of transcription start sites at single base resolution. This is achieved by enzymatically modifying the 5' triphosphorylated end of RNA with a selectable tag. We first applied Cappable-seq to E. coli, achieving up to 50 fold enrichment of primary transcripts and identifying an unprecedented 16539 transcription start sites (TSS) genome-wide at single base resolution. We also applied Cappable-seq to a mouse cecum sample and identified TSS in a microbiome. CONCLUSIONS:Cappable-seq allows for the first time the capture of the 5' end of primary transcripts. This enables a unique robust TSS determination in bacteria and microbiomes. In addition to and beyond TSS determination, Cappable-seq depletes ribosomal RNA and reduces the complexity of the transcriptome to a single quantifiable tag per transcript enabling digital profiling of gene expression in any microbiome.
Project description:We develop a method Re-Cappable-seq for determining eukaryotic transcription start sites derived from all RNA polymerases at nucleotide resolution. In particular, this method identifies the Pol-I and Pol-III TSSs, which are missing by CAGE. Applied to human A549 cell line, our method results in the identification of 33,468 and 5,269 high confidence Pol-II and non-Pol-II TSS respectively. Re-Cappable-seq identifies Pol-II TSS with higher specificity than CAGE. Overall design: We isolated total RNA from human A549 cancer cell line. First we used yDcpS to decap the canonical G-cap structure from Pol-II transcripts leaving a di-phosphorylated 5'end. Then we used VCE to specifically add a biotin cap to these di-phosphorylated 5'ends as well as the tri-phosphorylated 5'ends from the non-Pol-II transcripts. Finally we isolated these biotin capped RNA using streptavidin beads and sequenced using illumina. Here the RNA without streptavidin enrichment served as control. In addition, we also performed CIP treatment before decapping, which was used to distinguish the Pol-II and non-Pol-II transcripts.
Project description:BruUV-seq utilizes UV light to introduce transcription-blocking DNA lesions randomly in the genome prior to bromouridine-labeling and deep sequencing of nascent RNA. By inhibiting transcription elongation, but not initiation, pre-treatment with UV light leads to a redistribution of transcription reads resulting in the enhancement of nascent RNA signal towards the 5'-end of genes promoting the identification of transcription start sites (TSSs). Furthermore, transcripts associated with arrested RNA polymerases are protected from 3'-5' degradation and thus, unstable transcripts such as putative enhancer RNA (eRNA) are dramatically increased. Validation of BruUV-seq against GRO-cap that identifies capped run-on transcripts showed that most BruUV-seq peaks overlapped with GRO-cap signal over both TSSs and enhancer elements. Finally, BruUV-seq identified putative enhancer elements induced by tumor necrosis factor (TNF) treatment concomitant with expression of nearby TNF-induced genes. Taken together, BruUV-seq is a powerful new approach for identifying TSSs and active enhancer elements genome-wide in intact cells.
Project description:The position, shape and number of transcription start sites (TSS) are critical determinants of gene regulation. Most methods developed to detect TSSs and study promoter usage are, however, of limited use in studies that demand quantification of expression changes between two or more groups. In this study, we combine high-resolution detection of transcription start sites and differential expression analysis using a simplified TSS quantification protocol, MAPCap (Multiplexed Affinity Purification of Capped RNA) along with the software icetea . Applying MAPCap on developing Drosophila melanogaster embryos and larvae, we detected stage and sex-specific promoter and enhancer activity and quantify the effect of mutants of maleless (MLE) helicase at X-chromosomal promoters. We observe that MLE mutation leads to a median 1.9 fold drop in expression of X-chromosome promoters and affects the expression of several TSSs with a sexually dimorphic expression on autosomes. Our results provide quantitative insights into promoter activity during dosage compensation.
Project description:The multifunctional RNA-dependent RNA polymerase L protein of vesicular stomatitis virus catalyzes unconventional pre-mRNA capping via the covalent enzyme-pRNA intermediate formation, which requires the histidine-arginine (HR) motif in the polyribonucleotidyltransferase domain. Here, the effects of cap-defective mutations in the HR motif on transcription were analyzed using an in vitro reconstituted transcription system. The wild-type L protein synthesized the leader RNA from the 3'-end of the genome followed by 5'-capped and 3'-polyadenylated mRNAs from internal genes by a stop-start transcription mechanism. Cap-defective mutants efficiently produced the leader RNA, but displayed aberrant stop-start transcription using cryptic termination and initiation signals within the first gene, resulting in sequential generation of ?40-nucleotide transcripts with 5'-ATP from a correct mRNA-start site followed by a 28-nucleotide transcript and long 3'-polyadenylated transcript initiated with non-canonical GTP from atypical start sites. Frequent transcription termination and re-initiation within the first gene significantly attenuated the production of downstream mRNAs. Consistent with the inability of these mutants in in vitro mRNA synthesis and capping, these mutations were lethal to virus replication in cultured cells. These findings indicate that viral mRNA capping is required for accurate stop-start transcription as well as mRNA stability and translation and, therefore, for virus replication in host cells.
Project description:We develop a method SMRT-Cappable-seq that combines the isolation of unfragmented bacterial primary transcripts with the longread sequencing using PacBio. This method allows the identification and phasing of the transcrription start sites and the termination sites, thereby revealing the operon structure and the regulation of gene experession in bacteria. Applied to E.coli, our method results in an unprecedented definition of the transcriptome with 34% of the known operons from RegulonDB database being extended by at least one gene, and identifies a total of 2300 operons from which around 900 are novel. Overall design: Total RNAs were isolated from E. coli MG1655 cells grown under both M9 minimal and Rich condition. Primary transcripts were capped with desthiobiotin and extracted using streptavidin beads to form Enrich Library. While total RNAs without streptavidin enrichment were used to form Control Library. The RNAs were converted to cDNAs, then the cDNAs were amplified and sequenced using PacBio RSII and Sequel.
Project description:Identification of the transcription start sites (TSSs) of a virus is of great importance to understand and dissect the mechanism of viral genome transcription but this often requires costly and laborious experiments. Many segmented negative-sense RNA viruses (sNSVs) cleave capped leader sequences from a large variety of mRNAs and use these cleaved leaders as primers for transcription in a conserved process called cap snatching. The recent developments in high-throughput sequencing have made it possible to determine most, if not all, of the capped RNAs snatched by a sNSV. Here, we show that rice stripe tenuivirus (RSV), a plant-infecting sNSV, co-infects Nicotiana benthamiana with two different begomoviruses and snatches capped leader sequences from their mRNAs. By determining the 5' termini of a single RSV mRNA with high-throughput sequencing, the 5' ends of almost all the mRNAs of the co-infecting begomoviruses could be identified and mapped on their genomes. The findings in this study provide support for the using of the cap snatching of sNSVs as a tool to map viral TSSs.
Project description:It has recently been shown that RNA Polymerase II transcription is far more extensive than previously thought, much of it not associated with protein-coding genes. To investigate this phenomenon, we determined the genome-wide landscape of RNA Polymerase II transcription initiation and elongation in C. elegans. We identify 73,500 distinct clusters of transcription initiation and find that initiation is often bidirectional. Strikingly, the majority of initiation events occur in regions with enhancer-like chromatin signatures. We also assign transcription initiation sites to 7691 protein coding genes, the majority previously unknown because of trans-splicing. Through mapping RNA PolII initiation (short capped RNAs) and elongation (long capped RNAs), we provide identification of transcription start sites.