scholarly journals Origins and impacts of new exons

2014 ◽  
Author(s):  
Jason Merkin* ◽  
Ping Chen* ◽  
Maria Alexis ◽  
Sampsa Hautaniemi ◽  
Christopher Burge
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Nucleosome Occupancy ◽  
Mrna Levels ◽  
Sequencing Data ◽  
Protein Coding ◽  
Evolutionary Origins ◽  
Alternatively Spliced ◽  
Mammalian Genes ◽  
Species Specific

Mammalian genes are typically broken into several protein-coding and non-coding exons, but the evolutionary origins and functions of new exons are not well understood. Here, we analyzed patterns of exon gain using deep cDNA sequencing data from several mammals and one bird, identifying thousands of species- and lineage-specific exons. While exons conserved across mammals are mostly protein-coding and constitutively spliced, species-specific exons were mostly located in 5' untranslated regions and alternatively spliced. New exons most often derived from unique intronic sequence rather than repetitive elements, and were associated with upstream intronic deletions, increased nucleosome occupancy and RNA polymerase II pausing. Surprisingly, exon gain was associated with increased gene expression, but only in tissues where the exon was included, suggesting that splicing enhances steady-state mRNA levels and that changes in splicing represent a major contributor to the evolution of gene expression.

scholarly journals Commuting to Work: Nucleolar Long Non-Coding RNA Control Ribosome Biogenesis from Near and Far

2021 ◽  
Vol 7 (3) ◽  
pp. 42
Author(s):  
Victoria Mamontova ◽  
Barbara Trifault ◽  
Lea Boten ◽  
Kaspar Burger
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Ribosome Biogenesis ◽  
Intergenic Spacer ◽  
Cellular Growth ◽  
Rrna Synthesis ◽  
Protein Coding ◽  
Non Coding Rna ◽  
And Function ◽  
In Cis

Gene expression is an essential process for cellular growth, proliferation, and differentiation. The transcription of protein-coding genes and non-coding loci depends on RNA polymerases. Interestingly, numerous loci encode long non-coding (lnc)RNA transcripts that are transcribed by RNA polymerase II (RNAPII) and fine-tune the RNA metabolism. The nucleolus is a prime example of how different lncRNA species concomitantly regulate gene expression by facilitating the production and processing of ribosomal (r)RNA for ribosome biogenesis. Here, we summarise the current findings on how RNAPII influences nucleolar structure and function. We describe how RNAPII-dependent lncRNA can both promote nucleolar integrity and inhibit ribosomal (r)RNA synthesis by modulating the availability of rRNA synthesis factors in trans. Surprisingly, some lncRNA transcripts can directly originate from nucleolar loci and function in cis. The nucleolar intergenic spacer (IGS), for example, encodes nucleolar transcripts that counteract spurious rRNA synthesis in unperturbed cells. In response to DNA damage, RNAPII-dependent lncRNA originates directly at broken ribosomal (r)DNA loci and is processed into small ncRNA, possibly to modulate DNA repair. Thus, lncRNA-mediated regulation of nucleolar biology occurs by several modes of action and is more direct than anticipated, pointing to an intimate crosstalk of RNA metabolic events.

scholarly journals Characterization of the nuclear and cytosolic transcriptomes in human brain tissue reveals new insights into the subcellular distribution of RNA transcripts

2020 ◽  
Author(s):  
Ammar Zaghlool ◽  
Adnan Niazi ◽  
Åsa K. Björklund ◽  
Jakub Orzechowski Westholm ◽  
Adam Ameur ◽  
...  
Keyword(s):  
Gene Expression ◽  
Subcellular Localization ◽  
Human Brain ◽  
Expression Analysis ◽  
Differential Expression Analysis ◽  
Adult Brain ◽  
Sequencing Data ◽  
Human Brain Tissue ◽  
Protein Coding ◽  
The Impact

AbstractTranscriptome analysis has mainly relied on analyzing RNA sequencing data from whole cells, overlooking the impact of subcellular RNA localization and its influence on our understanding of gene function, and interpretation of gene expression signatures in cells. Here, we performed a comprehensive analysis of cytosolic and nuclear transcriptomes in human fetal and adult brain samples. We show significant differences in RNA expression for protein-coding and lncRNA genes between cytosol and nucleus. Transcripts displaying differential subcellular localization belong to particular functional categories and display tissue-specific localization patterns. We also show that transcripts encoding the nuclear-encoded mitochondrial proteins are significantly enriched in the cytosol compared to the rest of protein-coding genes. Further investigation of the use of the cytosolic or the nuclear transcriptome for differential gene expression analysis indicates important differences in results depending on the cellular compartment. These differences were manifested at the level of transcript types and the number of differentially expressed genes. Our data provide a resource of RNA subcellular localization in the human brain and highlight differences in using the cytosolic or the nuclear transcriptomes for differential expression analysis.

scholarly journals Codon usage is an important determinant of gene expression levels largely through its effects on transcription

2016 ◽  
Vol 113 (41) ◽  
pp. E6117-E6125 ◽  
Author(s):  
Zhipeng Zhou ◽  
Yunkun Dang ◽  
Mian Zhou ◽  
Lin Li ◽  
Chien-hung Yu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Codon Usage ◽  
Important Determinant ◽  
Mrna Translation ◽  
Mrna Levels ◽  
Protein Coding ◽  
Expression Levels ◽  
Highly Expressed Genes ◽  
The Impact ◽  
Gene Expression Levels

Codon usage biases are found in all eukaryotic and prokaryotic genomes, and preferred codons are more frequently used in highly expressed genes. The effects of codon usage on gene expression were previously thought to be mainly mediated by its impacts on translation. Here, we show that codon usage strongly correlates with both protein and mRNA levels genome-wide in the filamentous fungus Neurospora. Gene codon optimization also results in strong up-regulation of protein and RNA levels, suggesting that codon usage is an important determinant of gene expression. Surprisingly, we found that the impact of codon usage on gene expression results mainly from effects on transcription and is largely independent of mRNA translation and mRNA stability. Furthermore, we show that histone H3 lysine 9 trimethylation is one of the mechanisms responsible for the codon usage-mediated transcriptional silencing of some genes with nonoptimal codons. Together, these results uncovered an unexpected important role of codon usage in ORF sequences in determining transcription levels and suggest that codon biases are an adaptation of protein coding sequences to both transcription and translation machineries. Therefore, synonymous codons not only specify protein sequences and translation dynamics, but also help determine gene expression levels.

scholarly journals Codon choice directs constitutive mRNA levels in trypanosomes

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Janaina de Freitas Nascimento ◽  
Steven Kelly ◽  
Jack Sunter ◽  
Mark Carrington
Keyword(s):  
Gene Expression ◽  
Copy Number ◽  
Open Reading Frame ◽  
Mrna Turnover ◽  
Mrna Levels ◽  
Protein Coding ◽  
Reading Frame ◽  
Protein Coding Genes ◽  
The Relationship ◽  
Adaptation Index

Selective transcription of individual protein coding genes does not occur in trypanosomes and the cellular copy number of each mRNA must be determined post-transcriptionally. Here, we provide evidence that codon choice directs the levels of constitutively expressed mRNAs. First, a novel codon usage metric, the gene expression codon adaptation index (geCAI), was developed that maximised the relationship between codon choice and the measured abundance for a transcriptome. Second, geCAI predictions of mRNA levels were tested using differently coded GFP transgenes and were successful over a 25-fold range, similar to the variation in endogenous mRNAs. Third, translation was necessary for the accelerated mRNA turnover resulting from codon choice. Thus, in trypanosomes, the information determining the levels of most mRNAs resides in the open reading frame and translation is required to access this information.

scholarly journals The Paf1 complex broadly impacts the transcriptome ofSaccharomyces cerevisiae

2019 ◽  
Author(s):  
Mitchell A. Ellison ◽  
Alex R. Lederer ◽  
Marcie H. Warner ◽  
Travis Mavrich ◽  
Elizabeth A. Raupach ◽  
...  
Keyword(s):  
Gene Expression ◽  
De Novo ◽  
Differential Expression Analysis ◽  
Chromatin Modification ◽  
Antisense Transcription ◽  
Yeast Genome ◽  
Mrna Levels ◽  
Nascent Transcript ◽  
Protein Coding ◽  
Multiple Loci

ABSTRACTThe Polymerase Associated Factor 1 complex (Paf1C) is a multifunctional regulator of eukaryotic gene expression important for the coordination of transcription with chromatin modification and post-transcriptional processes. In this study, we investigated the extent to which the functions of Paf1C combine to regulate theSaccharomyces cerevisiaetranscriptome. While previous studies focused on the roles of Paf1C in controlling mRNA levels, here we took advantage of a genetic background that enriches for unstable transcripts and demonstrate that deletion ofPAF1affects all classes of Pol II transcripts including multiple classes of noncoding RNAs. By conducting ade novodifferential expression analysis independent of gene annotations, we found that Paf1 positively and negatively regulates antisense transcription at multiple loci. Comparisons with nascent transcript data revealed that many, but not all, changes in RNA levels detected by our analysis are due to changes in transcription instead of post-transcriptional events. To investigate the mechanisms by which Paf1 regulates protein-coding genes, we focused on genes involved in iron and phosphate homeostasis, which were differentially affected byPAF1deletion. Our results indicate that Paf1 stimulates phosphate gene expression through a mechanism that is independent of any individual Paf1C-dependent histone modification. In contrast, the inhibition of iron gene expression by Paf1 correlates with a defect in H3 K36 tri-methylation. Finally, we showed that one iron regulon gene,FET4, is coordinately controlled by Paf1 and transcription of upstream noncoding DNA. Together these data identify roles for Paf1C in controlling both coding and noncoding regions of the yeast genome.

scholarly journals Deregulation of a Cis-Acting lncRNA in Non-small Cell Lung Cancer May Control HMGA1 Expression

2021 ◽  
Vol 11 ◽  
Author(s):  
Greg L. Stewart ◽  
Adam P. Sage ◽  
Katey S. S. Enfield ◽  
Erin A. Marshall ◽  
David E. Cohn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Lung Cancer ◽  
Lung Epithelial Cells ◽  
Sequencing Data ◽  
Protein Coding ◽  
Cis Acting ◽  
Hmga1 Expression ◽  
Intervention Point ◽  
Cancer Phenotypes

BackgroundLong non-coding RNAs (lncRNAs) have long been implicated in cancer-associated phenotypes. Recently, a class of lncRNAs, known as cis-acting, have been shown to regulate the expression of neighboring protein-coding genes and may represent undiscovered therapeutic action points. The chromatin architecture modification gene HMGA1 has recently been described to be aberrantly expressed in lung adenocarcinoma (LUAD). However, the mechanisms mediating the expression of HMGA1 in LUAD remain unknown. Here we investigate the deregulation of a putative cis-acting lncRNA in LUAD, and its effect on the oncogene HMGA1.MethodsLncRNA expression was determined from RNA-sequencing data of tumor and matched non-malignant tissues from 36 LUAD patients. Transcripts with significantly deregulated expression were identified and validated in a secondary LUAD RNA-seq dataset (TCGA). SiRNA-mediated knockdown of a candidate cis-acting lncRNA was performed in BEAS-2B cells. Quantitative real-time PCR was used to observe the effects of lncRNA knockdown on the expression of HMGA1.ResultsWe identified the lncRNA RP11.513I15.6, which we refer to as HMGA1-lnc, neighboring HMGA1 to be significantly downregulated in both LUAD cohorts. Conversely, we found HMGA1 significantly overexpressed in LUAD and anticorrelated with HMGA1-lnc. In vitro experiments demonstrated siRNA-mediated inhibition of HMGA1-lnc in immortalized non-malignant lung epithelial cells resulted in a significant increase in HMGA1 gene expression.ConclusionOur results suggest that HMGA1-lnc is a novel cis-acting lncRNA that negatively regulates HMGA1 gene expression in lung cells. Further characterization of this regulatory mechanism may advance our understanding of the maintenance of lung cancer phenotypes and uncover a novel therapeutic intervention point for tumors driven by HMGA1.

scholarly journals Caffeine downregulates inflammatory pathways involved in autoimmunity

2017 ◽  
Author(s):  
Merve Iris ◽  
Pei-Suen Tsou ◽  
Amr H. Sawalha
Keyword(s):  
Gene Expression ◽  
Autoimmune Diseases ◽  
Mononuclear Cells ◽  
Expression Profiles ◽  
Mrna Levels ◽  
Sequencing Data ◽  
Inflammatory Genes ◽  
Pharmacologically Active ◽  
Dose Dependent ◽  
Validation Experiments

ABSTRACTObjectivesCaffeine is a widely consumed pharmacologically active product. In the present study, we focused on characterizing immunomodulatory effects of caffeine on peripheral blood mononuclear cells (PMBCs).MethodsThe effect of caffeine on gene expression profiles was initially evaluated using RNA sequencing data. Validation experiments were performed to confirm the results and examine dose-dependent effects of caffeine on PBMCs from healthy subjects. Gene expression levels were measured by real-time quantitative PCR, and cytokine production was determined using a multiplex cytokine assay.ResultsCaffeine at high doses showed a robust downregulatory effect of immune-related genes in PBMCs. Functional annotation analysis of downregulated genes revealed significant enrichment in cytokine activity and in genes related to several autoimmune diseases including lupus and rheumatoid arthritis. Dose-dependent validation experiments showed significant downregulation at the mRNA levels of key inflammatory genes including STAT1, TNF, and PPARG. TNF and PPARG were suppressed even with the lowest caffeine dose tested, which corresponds to the serum concentration of caffeine after administration of one cup of coffee. Cytokine levels of IL-8, MIP-1β, IL-6, IFN-γ, GM-CSF, TNF, IL-2, IL-4, MCP-1, and IL-10 were decreased significantly with caffeine treatment.ConclusionOur findings indicate potential downregulatory effects of caffeine on key inflammatory genes and cytokines, which play important role in autoimmunity. Further studies exploring therapeutic or disease-modulating potential of caffeine in autoimmune diseases and exploring the mechanisms involved are warranted.

scholarly journals Tissue- and Species-Specific Patterns of RNA metabolism in Post-Mortem Mammalian Retina and Retinal Pigment Epithelium

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Les Kallestad ◽  
Seth Blackshaw ◽  
Ahmad M. Khalil ◽  
Krzysztof Palczewski
Keyword(s):  
Gene Expression ◽  
Retinal Pigment Epithelium ◽  
Mrna Stability ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Rna Metabolism ◽  
Mrna Levels ◽  
Post Mortem ◽  
Accurate Analysis ◽  
Species Specific

Abstract Accurate analysis of gene expression in human tissues using RNA sequencing is dependent on the quality of source material. One major source of variation in mRNA quality is post-mortem time. While it is known that individual transcripts show differential post-mortem stability, few studies have directly and comprehensively analyzed mRNA stability following death, and in particular the extent to which tissue- and species-specific factors influence post-mortem mRNA stability are poorly understood. This knowledge is particularly important for ocular tissues studies, where tissues obtained post-mortem are frequently used for research or therapeutic applications. To directly investigate this question, we profiled mRNA levels in both neuroretina and retinal pigment epithelium (RPE) from mouse and baboon over a series of post-mortem intervals. We found substantial changes in gene expression as early as 15 minutes in the mouse and as early as three hours in the baboon eye tissues. Importantly, our findings demonstrate both tissue- and species- specific patterns of RNA metabolism, by identifying a set of genes that are either rapidly degraded or very stable in both species and/or tissues. Taken together, the data from this study lay the foundation for understanding RNA regulation post-mortem and provide novel insights into RNA metabolism in the tissues of the mammalian eye.

scholarly journals The evolution of sex-biased gene expression in the Drosophila brain

2020 ◽  
Author(s):  
Samuel Khodursky ◽  
Nicolas Svetec ◽  
Sylvia Durkin ◽  
Li Zhao
Keyword(s):  
Gene Expression ◽  
X Chromosome ◽  
Sexually Dimorphic ◽  
Evolution Of Sex ◽  
Sequencing Data ◽  
Regulatory Changes ◽  
Drosophila Brain ◽  
Expression Evolution ◽  
Species Specific ◽  
Flanking Regions

AbstractGenes with sex-biased expression in Drosophila are thought to underlie sexually dimorphic phenotypes and have been shown to possess important evolutionary properties. However, the forces and constraints governing the evolution of sex-biased genes in the somatic tissues of Drosophila are largely unknown. Using population-scale RNA sequencing data we show that sex-biased genes in the Drosophila brain are highly enriched on the X Chromosome and that most are biased in a species-specific manner. We show that X-linked male-biased genes, and to a lesser extent female-biased genes, are enriched for signatures of directional selection at the gene expression level. By examining the evolutionary properties of gene flanking regions on the X Chromosome, we find evidence that adaptive cis-regulatory changes are more likely to drive the expression evolution of X-linked male-biased genes than other X-linked genes. Finally, we examine whether constraint due to broad expression across multiple tissues and genetic constraint due to the largely shared male and female genomes could be responsible for the observed patterns of gene expression evolution. We find that expression breadth does not constrain the directional evolution of gene expression in the brain. Additionally, we find that the shared genome between males and females imposes a substantial constraint on the expression evolution of sex-biased genes. Overall, these results significantly advance our understanding of the patterns and forces shaping the evolution of sexual dimorphism in the Drosophila brain.

scholarly journals Flipping between Polycomb repressed and active transcriptional states introduces noise in gene expression

2017 ◽  
Author(s):  
Gozde Kar ◽  
Jong Kyoung Kim ◽  
Aleksandra A. Kolodziejczyk ◽  
Kedar Nath Natarajan ◽  
Elena Torlai Triglia ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Burst Size ◽  
Three Dimensions ◽  
Sequencing Data ◽  
Gene Expression Noise ◽  
Histone Modifiers ◽  
Transcriptional Bursting ◽  
Noise In Gene Expression ◽  
Active Genes

AbstractPolycomb repressive complexes (PRCs) are important histone modifiers, which silence gene expression, yet there exists a subset of PRC-bound genes actively transcribed by RNA polymerase II (RNAPII). It is likely that the role of PRC is to dampen expression of these PRC-active genes. However, it is unclear how this flipping between chromatin states alters the kinetics of transcriptional burst size and frequency relative to genes with exclusively activating marks. To investigate this, we integrate histone modifications and RNAPII states derived from bulk ChIP-seq data with single-cell RNA-sequencing data. We find that PRC-active genes have a greater cell-to-cell variation in expression than active genes with the same mean expression levels, and validate these results by knockout experiments. We also show that PRC-active genes are clustered on chromosomes in both two and three dimensions, and interactions with active enhancers promote a stabilization of gene expression noise. These findings provide new insights into how chromatin regulation modulates stochastic gene expression and transcriptional bursting, with implications for regulation of pluripotency and development.

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