Project description:To identify full-length cap-to-poly(A) mRNA isoforms of CD20 and rule out reverse transcription artifacts which are common in cDNA-seq approaches, long-read Oxford Nanopore direct RNA sequencing was performed on the Raji cell line.
Project description:Adenovirus is a common human pathogen that relies on host cell processes for transcription and processing of viral RNA and protein production. Although adenoviral promoters, splice junctions, and cleavage and polyadenylation sites have been characterized using low-throughput biochemical techniques or short read cDNA-based sequencing, these technologies do not fully capture the complexity of the adenoviral transcriptome. By combining Illumina short-read and nanopore long-read direct RNA sequencing approaches, we mapped transcription start sites and cleavage and polyadenylation sites across the adenovirus genome. In addition to confirming the known canonical viral early and late RNA cassettes, our analysis of splice junctions within long RNA reads revealed an additional 35 novel viral transcripts. These RNAs include fourteen new splice junctions which lead to expression of canonical open reading frames (ORF), six novel ORF-containing transcripts, and fifteen transcripts encoding for messages that potentially alter protein functions through truncations or fusion of canonical ORFs. In addition, we also detect RNAs that bypass canonical cleavage sites and generate potential chimeric proteins by linking separate gene transcription units. Of these, an evolutionary conserved protein was detected containing the N-terminus of E4orf6 fused to the downstream DBP/E2A ORF. Loss of this novel protein, E4orf6/DBP, was associated with aberrant viral replication center morphology and poor viral spread. Our work highlights how long-read sequencing technologies can reveal further complexity within viral transcriptomes.
Project description:We applied direct RNA long read sequencing for characterization of transcripts from constructs inserted into HEK293T mammalian cells with different promoters. Direct RNA sequencing was performed on an Oxford Nanopore GridION device using the Direct Sequencing Kit (SQK-RNA004, date accessed 15 May 2024), MinION RNA flow cell (FLO-MIN00RA), and data pre-processing was performed with MinKNOW (v24.06.10).
Project description:These experiments use a barcoded pool of reporter transcripts, each of which encode the same mScarlet-PPIG_LCD fusion protein, but using different degrees of GA-multivalency via codon bias, and containing a different number of constitutive introns. In order to be able to perform experiments using this pool, it was necessary to perform long-read sequencing of the plasmid pool to relate the barcodes in the 3' ends of the reporter to their gene structure. Therefore, we performed long-read sequencing of the plasmid pool (both the original pool used for transfection and the ePB plasmid used for PiggyBac integration). Furthermore, to determine the splicing patterns of the reporter genes, we transfected the plasmid pool into HeLa cells for 16 hours, then performed targeted long-read sequencing of the reporter plasmids via RT-PCR. Note: the Nanopore adapter ligation strategy means that reads can come in either orientation. To determine the gene architectures and barcodes, we used fuzzy string matching. First we matched to various fixed sequences throughout the reporter transcripts to determine the orientation of the read and that the read spanned the full length of the transcript. Then we used the same string matching strategy to detect the presence of the different intronic or exonic sequences - the gene architecture. Then we extracted the associated unique plasmid barcode associated with that gene architecture. Example reporter sequences can be found here: https://benchling.com/faraway/f_/kXCfddtQ-public-reporter-plasmid-maps/ or alternatively, in Supplemental Table 2 of the bioRxiv submission here: https://www.biorxiv.org/content/10.1101/2023.08.21.554177v1.supplementary-material
Project description:Evaluation of short-read-only, long-read-only, and hybrid assembly approaches on metagenomic samples demonstrating how they affect gene and protein prediction which is relevant for downstream functional analyses. For a human gut microbiome sample, we use complementary metatranscriptomic, and metaproteomic data to evaluate the metagenomic-based protein predictions.
Project description:Classically, mammalian mRNA and protein are thought to be encoded from a single genetic locus known as a gene. Whether mRNA can contain exons from geographically distinct genes to form chimeric mRNA in the absence of malignancy is widely unknown. Pervasive and naturally occurring chimeric mRNA could greatly expand the functional diversity of mammalian transcriptomes and potentially generate novel hybrid proteins that underpin diverse biological processes. Here we demonstrate that long-read direct RNA-seq, paired with targeted mRNA splice-isoform analysis, enables the identification of a plethora of dynamically regulated chimeric mRNA in innate immune cells.
Project description:Eukaryotic mRNA is classically expected to be monocistronic, linear, and encoded by a single defined genetic locus. Conversely, emerging evidence has identified bicistronic translation and circularized mRNA as pervasive unconventional features of mammalian transcriptomes. During oncogenic translocation in humans, DNA from distinct genes can fuse together and encode chimeric mRNAs that directly contribute to tumorigenesis. However, it remains widely unknown whether or not chimeric mRNAs exist in the absence of chromosomal rearrangements, and if they contribute to normal physiological processes. To assay for chimeric mRNA (chRNA) expression in mammalian innate immune cells while circumventing chRNA detection limitations associated with conventional RNA-sequencing (RNA-seq) technology, including read fragmentation and artifact generation by template switching, we performed long read direct RNA sequencing (LR-DRS) of differentially polarized bone marrow-derived macrophages (BMDMs) using the Oxford Nanopore platform.