Combinatorial Pattern of Histone Modifications in Exon Skipping Event.
Ontology highlight
ABSTRACT:
SUBMITTER: Chen W
PROVIDER: S-EPMC6387913 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Alternative splicing (AS) not only ensures the diversity of gene expression products, but also closely correlated with genetic diseases. Therefore, knowledge about regulatory mechanisms of AS will provide useful clues for understanding its biological functions. In the current study, a random forest based method was developed to classify included and excluded exons in exon skipping event. In this method, the samples in the dataset were encoded by using optimal histone modification features which were optimized by using the Maximum Relevance Maximum Distance (MRMD) feature selection technique. The proposed method obtained an accuracy of 72.91% in 10-fold cross validation test and outperformed existing methods. Meanwhile, we also systematically analyzed the distribution of histone modifications between included and excluded exons and discovered their preference in both kinds of exons, which might provide insights into researches on the regulatory mechanisms of alternative splicing.
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Project description:Many genes increase coding capacity by alternate exon usage. The gene encoding the insect nicotinic acetylcholine receptor (nAChR) α6 subunit, target of the bio-insecticide spinosad, is one example of this and expands protein diversity via alternative splicing of mutually exclusive exons. Here, we show that spinosad resistance in the tomato leaf miner, Tuta absoluta is associated with aberrant regulation of splicing of Taα6 resulting in a novel form of insecticide resistance mediated by exon skipping. Sequencing of the α6 subunit cDNA from spinosad selected and unselected strains of T. absoluta revealed all Taα6 transcripts of the selected strain were devoid of exon 3, with comparison of genomic DNA and mRNA revealing this is a result of exon skipping. Exon skipping cosegregated with spinosad resistance in survival bioassays, and functional characterization of this alteration using modified human nAChR α7, a model of insect α6, demonstrated that exon 3 is essential for receptor function and hence spinosad sensitivity. DNA and RNA sequencing analyses suggested that exon skipping did not result from genetic alterations in intronic or exonic cis-regulatory elements, but rather was associated with a single epigenetic modification downstream of exon 3a, and quantitative changes in the expression of trans-acting proteins that have known roles in the regulation of alternative splicing. Our results demonstrate that the intrinsic capacity of the α6 gene to generate transcript diversity via alternative splicing can be readily exploited during the evolution of resistance and identifies exon skipping as a molecular alteration conferring insecticide resistance.
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Project description:Exon skipping (ES) is reported to be the most common alternative splicing event due to loss of functional domains/sites or shifting of the open reading frame (ORF), leading to a variety of human diseases and considered therapeutic targets. To date, systematic and intensive annotations of ES events based on the skipped exon units in cancer and normal tissues are not available. Here, we built ExonSkipDB, the ES annotation database available at https://ccsm.uth.edu/ExonSkipDB/, aiming to provide a resource and reference for functional annotation of ES events in multiple cancer and tissues to identify therapeutically targetable genes in individual exon units. We collected 14 272 genes that have 90 616 and 89 845 ES events across 33 cancer types and 31 normal tissues from The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx). For the ES events, we performed multiple functional annotations. These include ORF assignment of exon skipped transcript, studies of lost protein functional features due to ES events, and studies of exon skipping events associated with mutations and methylations based on multi-omics evidence. ExonSkipDB will be a unique resource for cancer and drug research communities to identify therapeutically targetable exon skipping events.
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Project description:Histones undergo numerous covalent modifications that play important roles in regulating gene expression. Previous investigations have focused on the effects of histone modifications on gene promoters, whereas efforts to unravel their effects on transcribed regions have lagged behind. To elucidate the effects of histone modification on transcribed regions, we constructed a quantitative model, which we suggest can predict the variation of gene expression more faithfully than the model constructed on promoters. Moreover, motivated by the fact that exon spicing is functionally coupled to transcription, we also devised a quantitative model to predict alternative exon expression using histone modifications on exons. This model was found to be general across different exon types and even cell types. Furthermore, an interaction network linking histone modifications to alternative exon expression was constructed using partial correlations. The network indicated that gene expression and specific histone modifications (H3K36me3 and H4K20me1) could directly influence the exon expression, while other modifications could act in an additive way to account for the stability and robustness. In addition, our results suggest that combinations of histone modifications contribute to exon splicing in a redundant and cumulative fashion. To conclude, this study provides a better understanding of the effects of histone modifications on gene transcribed regions.
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Project description:Splicing is a complex process regulated by sequence at the classical splice sites and other motifs in exons and introns with an enhancing or silencing effect. In addition, specific histone modifications on nucleosomes positioned over the exons have been shown to correlate both positively and negatively with exon expression. Here, we trained a model of "IF … THEN …" rules to predict exon inclusion levels in a transcript from histone modification patterns. Furthermore, we showed that combinations of histone modifications, in particular those residing on nucleosomes preceding or succeeding the exon, are better predictors of exon inclusion levels than single modifications. The resulting model was evaluated with cross validation and had an average accuracy of 72% for 27% of the exons, which demonstrates that epigenetic signals substantially mark alternative splicing.
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Project description:Antisense-mediated exon skipping is one of the most promising therapeutic strategies for Duchenne muscular dystrophy (DMD), and some antisense oligonucleotide (ASO) drugs have already been approved by the US FDA despite their low efficacy. The potential of this therapy is still limited by several challenges, including the reduced expression of the dystrophin transcript and the strong 5'-3' imbalance in mutated transcripts. We therefore hypothesize that increasing histone acetylation using histone deacetylase inhibitors (HDACi) could correct the transcript imbalance, offering more available pre-mRNA target and ultimately increasing dystrophin rescue. Here, we evaluated the impact of such a combined therapy on the Dmd transcript imbalance phenomenon and on dystrophin restoration levels in mdx mice. Analysis of the Dmd transcript levels at different exon-exon junctions revealed a tendency to correct the 5'-3' imbalance phenomenon following treatment with HDACi. Significantly higher levels of dystrophin restoration (up to 74% increase) were obtained with givinostat and valproic acid compared with mice treated with ASO alone. Additionally, we demonstrate an increase in H3K9 acetylation in human myocytes after treatment with valproic acid. These findings indicate that HDACi can improve the therapeutic potential of exon-skipping approaches, offering promising perspectives for the treatment of DMD.
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Project description:The study of histone modifications and their interaction with effector modules/proteins has attracted increasing attention in recent years. Accumulating evidence indicates that epigenetic regulation, which involves post-translational modification on histones and DNAs or the participation of RNAs, plays an important role in many cellular processes. Histone modifications can function individually but are also capable of functioning combinatorially as a pattern. Recently, much more attention has focused on interpreting combined histone patterns by their downstream effectors. Structure/function-based studies on paired module-mediated histone cross-talk have greatly enhanced our understanding of the plasticity of the "histone code" hypothesis.
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Project description:Increasing evidence suggests that histone posttranslational modifications (PTMs) function in a combinatorial fashion to regulate the diverse activities associated with chromatin. Yet how these patterns of histone PTMs influence the adapter proteins known to bind them is poorly understood. In addition, how histone-specific antibodies are influenced by these same patterns of PTMs is largely unknown. Here we examine the binding properties of histone-specific antibodies and histone-interacting proteins using peptide arrays containing a library of combinatorially modified histone peptides. We find that modification-specific antibodies are more promiscuous in their PTM recognition than expected and are highly influenced by neighboring PTMs. Furthermore, we find that the binding of histone-interaction domains from BPTF, CHD1, and RAG2 to H3 lysine 4 trimethylation is also influenced by combinatorial PTMs. These results provide further support for the histone code hypothesis and raise specific concerns with the quality of the currently available modification-specific histone antibodies.
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Project description:Alternative splicing (AS) is frequent during early mouse embryonic development. Specific histone post-translational modifications (hPTMs) have been shown to regulate exon splicing by either directly recruiting splice machinery or indirectly modulating transcriptional elongation. In this study, we hypothesized that hPTMs regulate expression of alternatively spliced genes for specific processes during differentiation. To address this notion, we applied an innovative machine learning approach to relate global hPTM enrichment to AS regulation during mammalian tissue development. We found that specific hPTMs, H3K36me3 and H3K4me1, play a role in skipped exon selection among all the tissues and developmental time points examined. In addition, we used iterative random forest model and found that interactions of multiple hPTMs most strongly predicted splicing when they included H3K36me3 and H3K4me1. Collectively, our data demonstrated a link between hPTMs and alternative splicing which will drive further experimental studies on the functional relevance of these modifications to alternative splicing.
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Project description:A compelling body of literature, based on next generation chromatin immunoprecipitation and RNA sequencing of reward brain regions indicates that the regulation of the epigenetic landscape likely underlies chronic drug abuse and addiction. It is now critical to develop highly innovative computational strategies to reveal the relevant regulatory transcriptional mechanisms that may underlie neuropsychiatric disease. We have analyzed chromatin regulation of alternative splicing, which is implicated in cocaine exposure in mice. Recent literature has described chromatin-regulated alternative splicing, suggesting a novel function for drug-induced neuroepigenetic remodeling. However, the extent of the genome-wide association between particular histone modifications and alternative splicing remains unexplored. To address this, we have developed novel computational approaches to model the association between alternative splicing and histone posttranslational modifications in the nucleus accumbens (NAc), a brain reward region. Using classical statistical methods and machine learning to combine ChIP-Seq and RNA-Seq data, we found that specific histone modifications are strongly associated with various aspects of differential splicing. H3K36me3 and H3K4me1 have the strongest association with splicing indicating they play a significant role in alternative splicing in brain reward tissue.
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