Extensive alternative polyadenylation during zebrafish development

The post-transcriptional fate of messenger RNAs (mRNAs) is largely dictated by their 3′ untranslated regions (3′ UTRs), which are defined by cleavage and polyadenylation (CPA) of pre-mRNAs. We used poly(A)-position profiling by sequencing (3P-seq) to map poly(A) sites at eight developmental stages and tissues in the zebrafish. Analysis of over 60 million 3P-seq reads substantially increased and improved existing 3′ UTR annotations, resulting in confidently identified 3′ UTRs for >79% of the annotated protein-coding genes in zebrafish. mRNAs from most zebrafish genes undergo alternative CPA, with those from more than a thousand genes using different dominant 3′ UTRs at different stages. These included one of the poly(A) polymerase genes, for which alternative CPA reinforces its repression in the ovary. 3′ UTRs tend to be shortest in the ovaries and longest in the brain. Isoforms with some of the shortest 3′ UTRs are highly expressed in the ovary, yet absent in the maternally contributed RNAs of the embryo, perhaps because their 3′ UTRs are too short to accommodate a uridine-rich motif required for stability of the maternal mRNA. At 2 h post-fertilization, thousands of unique poly(A) sites appear at locations lacking a typical polyadenylation signal, which suggests a wave of widespread cytoplasmic polyadenylation of mRNA degradation intermediates. Our insights into the identities, formation, and evolution of zebrafish 3′ UTRs provide a resource for studying gene regulation during vertebrate development.National Institutes of Health (U.S.) (Grant GM067031)

Comparison and calibration of transcriptome data from RNA-Seq and tiling arrays

<p>Abstract</p> <p>Background</p> <p>Tiling arrays have been the tool of choice for probing an organism's transcriptome without prior assumptions about the transcribed regions, but RNA-Seq is becoming a viable alternative as the costs of sequencing continue to decrease. Understanding the relative merits of these technologies will help researchers select the appropriate technology for their needs.</p> <p>Results</p> <p>Here, we compare these two platforms using a matched sample of poly(A)-enriched RNA isolated from the second larval stage of <it>C. elegans</it>. We find that the raw signals from these two technologies are reasonably well correlated but that RNA-Seq outperforms tiling arrays in several respects, notably in exon boundary detection and dynamic range of expression. By exploring the accuracy of sequencing as a function of depth of coverage, we found that about 4 million reads are required to match the sensitivity of two tiling array replicates. The effects of cross-hybridization were analyzed using a "nearest neighbor" classifier applied to array probes; we describe a method for determining potential "black list" regions whose signals are unreliable. Finally, we propose a strategy for using RNA-Seq data as a gold standard set to calibrate tiling array data. All tiling array and RNA-Seq data sets have been submitted to the modENCODE Data Coordinating Center.</p> <p>Conclusions</p> <p>Tiling arrays effectively detect transcript expression levels at a low cost for many species while RNA-Seq provides greater accuracy in several regards. Researchers will need to carefully select the technology appropriate to the biological investigations they are undertaking. It will also be important to reconsider a comparison such as ours as sequencing technologies continue to evolve.</p

Global Analyses of the Effect of Different Cellular Contexts on MicroRNA Targeting

MicroRNA (miRNA) regulation clearly impacts animal development, but the extent to which development—with its resulting diversity of cellular contexts—impacts miRNA regulation is unclear. Here, we compared cohorts of genes repressed by the same miRNAs in different cell lines and tissues and found that target repertoires were largely unaffected, with secondary effects explaining most of the differential responses detected. Outliers resulting from differential direct targeting were often attributable to alternative 3′ UTR isoform usage that modulated the presence of miRNA sites. More inclusive examination of alternative 3′ UTR isoforms revealed that they influence ~10% of predicted targets when comparing any two cell types. Indeed, considering alternative 3′ UTR isoform usage improved prediction of targeting efficacy significantly beyond the improvements observed when considering constitutive isoform usage. Thus, although miRNA targeting is remarkably consistent in different cell types, considering the 3′ UTR landscape helps predict targeting efficacy and explain differential regulation that is observed.Korea (South). Ministry of Education, Science and Technology (MEST) (National Research Foundation of Korea. NRF-2013R1A1A1010185)National Institutes of Health (U.S.) (Grant RO1 GM067031)National Institutes of Health (U.S.) (Grant K99 GM102319)National Science Foundation (U.S.). Graduate Research Fellowship Progra

High-throughput sequencing of RNA 5'- and 3'-termini yields insights into viral and vertebrate gene expression

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2015.Cataloged from PDF version of thesis.Includes bibliographical references.Next-generation sequencing techniques are unparalleled in their resolution and dynamic range, but are limited by read depletion at transcript ends. Protocols that specifically target these ends overcome this limitation and enable the study of biological phenomena that would otherwise prove refractory to RNA-Seq. Here, we use two such techniques to study heterogeneous sequences at the 5' ends of influenza transcripts and alternative polyadenylation at the 3' ends of vertebrate transcripts. The 5' ends of influenza mRNAs include heterogeneous sequences derived from host RNAs. In a process termed cap snatching, the viral polymerase cleaves host RNAs ~10-13 nucleotides downstream of their caps and uses the resulting fragments to prime viral transcription. High-throughput 5' rapid amplification of cDNA ends resulted in 54 million chimeric reads containing host-derived leaders. These sequences provided evidence for stuttering during transcription initiation and an influence of the viral template on the extent of realignment. Accounting for realignment suggested a common preference by the polymerase irrespective of the viral template, and suggested that a single base pair is sufficient to prime transcription. Mapping trimmed leaders to annotated transcription start sites (TSSs) revealed that the most abundant leaders correspond to small nuclear RNAs, consistent with cap snatching of nascent transcripts. The 3' ends of mRNAs are generally appended with a poly(A) tail, but alternative polyadenylation sites may vary depending on cellular context. 3P-Seq is a method that specifically captures alternative polyadenylation sites without relying on oligo(dT) priming, which may cause artifacts. Applying 3P-Seq to eukaryotic model organisms improved their gene annotations and provided insight into targeting by microRNAs, a class of ~21-23 nucleotide RNAs that mediate mRNA destabilization. The isoform ratios of transcripts containing miR-155 sites were predictive of the extent to which these transcripts would respond to miR-155 transfection. Conversely, knocking out miR-22 in mice specifically upregulated isoforms containing miR-22 sites, suggesting that microRNAs reciprocally affect the 3'-UTR landscape. Lastly, analysis of other datasets derived from zebrafish embryos revealed broad lengthening of 3'-UTR isoforms during development and noncanonical polyadenylation during the maternal-to-zygotic transition.by David N.P. Koppstein.Ph. D

Principles of Long Noncoding RNA Evolution Derived from Direct Comparison of Transcriptomes in 17 Species Cell Reports Resource Principles of Long Noncoding RNA Evolution Derived from Direct Comparison of Transcriptomes in 17 Species

Graphical Abstract Highlights SUMMARY The inability to predict long noncoding RNAs from genomic sequence has impeded the use of comparative genomics for studying their biology. Here, we develop methods that use RNA sequencing (RNAseq) data to annotate the transcriptomes of 16 vertebrates and the echinoid sea urchin, uncovering thousands of previously unannotated genes, most of which produce long intervening noncoding RNAs (lincRNAs). Although in each species, &gt;70% of lincRNAs cannot be traced to homologs in species that diverged &gt;50 million years ago, thousands of human lincRNAs have homologs with similar expression patterns in other species. These homologs share short, 5 0 -biased patches of sequence conservation nested in exonic architectures that have been extensively rewired, in part by transposable element exonization. Thus, over a thousand human lincRNAs are likely to have conserved functions in mammals, and hundreds beyond mammals, but those functions require only short patches of specific sequences and can tolerate major changes in gene architecture

Principles of Long Noncoding RNA Evolution Derived from Direct Comparison of Transcriptomes in 17 Species

The inability to predict long noncoding RNAs from genomic sequence has impeded the use of comparative genomics for studying their biology. Here, we develop methods that use RNA sequencing (RNA-seq) data to annotate the transcriptomes of 16 vertebrates and the echinoid sea urchin, uncovering thousands of previously unannotated genes, most of which produce long intervening noncoding RNAs (lincRNAs). Although in each species, >70% of lincRNAs cannot be traced to homologs in species that diverged >50 million years ago, thousands of human lincRNAs have homologs with similar expression patterns in other species. These homologs share short, 5′-biased patches of sequence conservation nested in exonic architectures that have been extensively rewired, in part by transposable element exonization. Thus, over a thousand human lincRNAs are likely to have conserved functions in mammals, and hundreds beyond mammals, but those functions require only short patches of specific sequences and can tolerate major changes in gene architecture

The RNA polymerase "switch region" is a target for inhibitors

The alpha-pyrone antibiotic myxopyronin (Myx) inhibits bacterial RNA polymerase (RNAP). Here, through a combination of genetic, biochemical, and structural approaches, we show that Myx interacts with the RNAP "switch region"--the hinge that mediates opening and closing of the RNAP active center cleft--to prevent interaction of RNAP with promoter DNA. We define the contacts between Myx and RNAP and the effects of Myx on RNAP conformation and propose that Myx functions by interfering with opening of the RNAP active-center cleft during transcription initiation. We further show that the structurally related alpha-pyrone antibiotic corallopyronin (Cor) and the structurally unrelated macrocyclic-lactone antibiotic ripostatin (Rip) function analogously to Myx. The RNAP switch region is distant from targets of previously characterized RNAP inhibitors, and, correspondingly, Myx, Cor, and Rip do not exhibit crossresistance with previously characterized RNAP inhibitors. The RNAP switch region is an attractive target for identification of new broad-spectrum antibacterial therapeutic agents.status: publishe

Lymphoma driver mutations in the pathogenic evolution of an iconic human autoantibody

Pathogenic autoantibodies arise in many autoimmune diseases, but it is not understood how the cells making them evade immune checkpoints. Here, single-cell multi-omics analysis demonstrates a shared mechanism with lymphoid malignancy in the formation of public rheumatoid factor autoantibodies responsible for mixed cryoglobulinemic vasculitis. By combining single-cell DNA and RNA sequencing with serum antibody peptide sequencing and antibody synthesis, rare circulating B lymphocytes making pathogenic autoantibodies were found to comprise clonal trees accumulating mutations. Lymphoma driver mutations in genes regulating B cell proliferation and V(D)J mutation (CARD11, TNFAIP3, CCND3, ID3, BTG2, and KLHL6) were present in rogue B cells producing the pathogenic autoantibody. Antibody V(D)J mutations conferred pathogenicity by causing the antigen-bound autoantibodies to undergo phase transition to insoluble aggregates at lower temperatures. These results reveal a pre-neoplastic stage in human lymphomagenesis and a cascade of somatic mutations leading to an iconic pathogenic autoantibody