SpliceTools, a suite of downstream RNA splicing analysis tools to investigate mechanisms and impact of alternative splicing

PerturbAtlas: a comprehensive atlas of public genetic perturbation bulk RNA-seq datasets

Manipulating gene expression is crucial for understanding gene function, with high-throughput sequencing techniques such as RNA-seq elucidating the downstream mechanisms involved. However, the lack of a standardized metadata format for small-scale perturbation expression datasets in public repositories hinders their reuse. To address this issue, we developed PerturbAtlas, an add-value resource that re-analyzes publicly archived RNA-seq libraries to provide quantitative data on gene expression, transcript profiles, and alternative splicing events following genetic perturbation. PerturbAtlas assists users in identifying trends at the gene and isoform levels in perturbation assays by re-analyzing a curated set of 122 801 RNA-seq libraries across 13 species. This resource is freely available at https://perturbatlas.kratoss.site as both raw data tables and an interactive browser, allowing searches by species, tissue or genomic features. The results provide detailed information on alterations following perturbations, accessible through both forward and reverse approaches, thereby enabling the exploration of perturbation consequences and the identification of potential causal perturbations.

Role of long noncoding RNAs in the regulation of alternative splicing in glioblastoma

Glioblastoma multiforme (GBM) is a highly severe primary brain tumor. Despite extensive research, effective treatments remain elusive. Long noncoding RNAs (lncRNAs) play a significant role in both cancer and normal biology. They influence alternative splicing (AS), which is crucial in cancer. Advances in lncRNA-specific microarrays and next-generation sequencing have enhanced understanding of AS. Abnormal AS contributes to cancer invasion, metastasis, apoptosis, therapeutic resistance, and tumor development, including glioma. lncRNA-mediated AS affects several cellular signaling pathways, promoting or suppressing cancer malignancy. This review discusses the lncRNAs regulating AS in glioblastoma and their mechanisms.

Variation of C-terminal domain governs RNA polymerase II genomic locations and alternative splicing in eukaryotic transcription

The C-terminal domain of RPB1 (CTD) orchestrates transcription by recruiting regulators to RNA Pol II upon phosphorylation. With CTD driving condensate formation on gene loci, the molecular mechanism behind how CTD-mediated recruitment of transcriptional regulators influences condensates formation remains unclear. Our study unveils that phosphorylation reversibly dissolves phase separation induced by the unphosphorylated CTD. Phosphorylated CTD, upon specific association with transcription regulators, forms distinct condensates from unphosphorylated CTD. Functional studies demonstrate CTD variants with diverse condensation properties exhibit differences in promoter binding and mRNA co-processing in cells. Notably, varying CTD lengths influence the assembly of RNA processing machinery and alternative splicing outcomes, which in turn affects cellular growth, linking the evolution of CTD variation/length with the complexity of splicing from yeast to human. These findings provide compelling evidence for a model wherein post-translational modification enables the transition of functionally specialized condensates, highlighting a co-evolution link between CTD condensation and splicing.

splicekit: an integrative toolkit for splicing analysis from short-read RNA-seq

Motivation

Analysis of alternative splicing using short-read RNA-seq data is a complex process that involves several steps: alignment of reads to the reference genome, identification of alternatively spliced features, motif discovery, analysis of RNA-protein binding near donor and acceptor splice sites, and exploratory data visualization. To the best of our knowledge, there is currently no integrative open-source software dedicated to this task.

Results

Here, we introduce splicekit, a Python package that provides and integrates a set of existing and novel splicing analysis tools for conducting splicing analysis.

Availability and implementation

The software splicekit is open-source and available at Github (https://github.com/bedapub/splicekit) and via the Python Package Index.

Variation of C-terminal domain governs RNA polymerase II genomic locations and alternative splicing in eukaryotic transcription

The C-terminal domain of RPB1 (CTD) orchestrates transcription by recruiting regulators to RNA Pol II upon phosphorylation. Recent insights highlight the pivotal role of CTD in driving condensate formation on gene loci. Yet, the molecular mechanism behind how CTD-mediated recruitment of transcriptional regulators influences condensates formation remains unclear. Our study unveils that phosphorylation reversibly dissolves phase separation induced by the unphosphorylated CTD. Phosphorylated CTD, upon specific association with transcription regulatory proteins, forms distinct condensates from unphosphorylated CTD. Function studies demonstrate CTD variants with diverse condensation properties in vitro exhibit difference in promoter binding and mRNA co-processing in cells. Notably, varying CTD lengths lead to alternative splicing outcomes impacting cellular growth, linking the evolution of CTD variation/length with the complexity of splicing from yeast to human. These findings provide compelling evidence for a model wherein post-translational modification enables the transition of functionally specialized condensates, highlighting a co-evolution link between CTD condensation and splicing.

Alternative Transcripts Diversify Genome Function for Phenome Relevance to Health and Diseases

Manipulation using alternative exon splicing (AES), alternative transcription start (ATS), and alternative polyadenylation (APA) sites are key to transcript diversity underlying health and disease. All three are pervasive in organisms, present in at least 50% of human protein-coding genes. In fact, ATS and APA site use has the highest impact on protein identity, with their ability to alter which first and last exons are utilized as well as impacting stability and translation efficiency. These RNA variants have been shown to be highly specific, both in tissue type and stage, with demonstrated importance to cell proliferation, differentiation and the transition from fetal to adult cells. While alternative exon splicing has a limited effect on protein identity, its ubiquity highlights the importance of these minor alterations, which can alter other features such as localization. The three processes are also highly interwoven, with overlapping, complementary, and competing factors, RNA polymerase II and its CTD (C-terminal domain) chief among them. Their role in development means dysregulation leads to a wide variety of disorders and cancers, with some forms of disease disproportionately affected by specific mechanisms (AES, ATS, or APA). Challenges associated with the genome-wide profiling of RNA variants and their potential solutions are also discussed in this review.

Bromodomain-containing Protein 4 regulates innate inflammation via modulation of alternative splicing

Introduction

Bromodomain-containing Protein 4 (BRD4) is a transcriptional regulator which coordinates gene expression programs controlling cancer biology, inflammation, and fibrosis. In the context of airway viral infection, BRD4-specific inhibitors (BRD4i) block the release of pro-inflammatory cytokines and prevent downstream epithelial plasticity. Although the chromatin modifying functions of BRD4 in inducible gene expression have been extensively investigated, its roles in post-transcriptional regulation are not well understood. Given BRD4's interaction with the transcriptional elongation complex and spliceosome, we hypothesize that BRD4 is a functional regulator of mRNA processing.

Methods

To address this question, we combine data-independent analysis - parallel accumulation-serial fragmentation (diaPASEF) with RNA-sequencing to achieve deep and integrated coverage of the proteomic and transcriptomic landscapes of human small airway epithelial cells exposed to viral challenge and treated with BRD4i.

Results

We discover that BRD4 regulates alternative splicing of key genes, including Interferon-related Developmental Regulator 1 (IFRD1) and X-Box Binding Protein 1 (XBP1), related to the innate immune response and the unfolded protein response (UPR). We identify requirement of BRD4 for expression of serine-arginine splicing factors, splicosome components and the Inositol-Requiring Enzyme 1 IREα affecting immediate early innate response and the UPR.

Discussion

These findings extend the transcriptional elongation-facilitating actions of BRD4 in control of post-transcriptional RNA processing via modulating splicing factor expression in virus-induced innate signaling.