scholarly journals Crosstalk between codon optimality and cis-regulatory elements dictates mRNA stability

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Santiago Gerardo Medina-Muñoz ◽  
Gopal Kushawah ◽  
Luciana Andrea Castellano ◽  
Michay Diez ◽  
Michelle Lynn DeVore ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mrna Stability ◽  
Messenger Rna ◽  
Developmental Trajectories ◽  
Regulatory Elements ◽  
Early Embryo ◽  
Regulatory Sequences ◽  
Dependent Manner ◽  
Optimal Codons ◽  
Major Predictor

Abstract Background The regulation of messenger RNA (mRNA) stability has a profound impact on gene expression dynamics during embryogenesis. For example, in animals, maternally deposited mRNAs are degraded after fertilization to enable new developmental trajectories. Regulatory sequences in 3′ untranslated regions (3′UTRs) have long been considered the central determinants of mRNA stability. However, recent work indicates that the coding sequence also possesses regulatory information. Specifically, translation in cis impacts mRNA stability in a codon-dependent manner. However, the strength of this mechanism during embryogenesis, as well as its relationship with other known regulatory elements, such as microRNA, remains unclear. Results Here, we show that codon composition is a major predictor of mRNA stability in the early embryo. We show that this mechanism works in combination with other cis-regulatory elements to dictate mRNA stability in zebrafish and Xenopus embryos as well as in mouse and human cells. Furthermore, we show that microRNA targeting efficacy can be affected by substantial enrichment of optimal (stabilizing) or non-optimal (destabilizing) codons. Lastly, we find that one microRNA, miR-430, antagonizes the stabilizing effect of optimal codons during early embryogenesis in zebrafish. Conclusions By integrating the contributions of different regulatory mechanisms, our work provides a framework for understanding how combinatorial control of mRNA stability shapes the gene expression landscape.

scholarly journals iCodon: ideal codon design for customized gene expression

2021 ◽  
Author(s):  
Ariel Bazzini
Keyword(s):  
Gene Expression ◽  
Mrna Stability ◽  
Messenger Rna ◽  
Synonymous Codon ◽  
Biological Research ◽  
Dependent Manner ◽  
Coding Sequence ◽  
Expression Levels ◽  
Codon Composition ◽  
Wide Range

Abstract Messenger RNA (mRNA) stability substantially impacts steady-state gene expression levels in a cell. mRNA stability, in turn, is strongly affected by codon composition in a translation dependent manner across species, through a mechanism termed codon optimality. We have developed iCodon (www.iCodon.org), an algorithm for customizing mRNA expression through the introduction of synonymous codon substitutions into the coding sequence. iCodon is optimized for four vertebrate transcriptomes: mouse, human, frog, and fish. Users can predict the mRNA stability of any coding sequence based on its codon composition and subsequently generate more stable (optimized) or unstable (deoptimized) variants encoding for the same protein. Further, we show that codon optimality predictions correlate with expression levels using fluorescent reporters and endogenous genes in human cells and zebrafish embryos. Therefore, iCodon will benefit basic biological research, as well as a wide range of applications for biotechnology and biomedicine.

scholarly journals iCodon: ideal codon design for customized gene expression

2021 ◽  
Author(s):  
Santiago Medina-Munoz ◽  
Michay Diez ◽  
Luciana Castellano ◽  
Gabriel da Silva Pescador ◽  
Qiushuang Wu ◽  
...  
Keyword(s):  
Gene Expression ◽  
Mrna Stability ◽  
Messenger Rna ◽  
Synonymous Codon ◽  
Biological Research ◽  
Dependent Manner ◽  
Coding Sequence ◽  
Expression Levels ◽  
Codon Composition ◽  
Wide Range

Messenger RNA (mRNA) stability substantially impacts steady-state gene expression levels in a cell. mRNA stability, in turn, is strongly affected by codon composition in a translation-dependent manner across species, through a mechanism termed codon optimality. We have developed iCodon (www.iCodon.org), an algorithm for customizing mRNA expression through the introduction of synonymous codon substitutions into the coding sequence. iCodon is optimized for four vertebrate transcriptomes: mouse, human, frog, and fish. Users can predict the mRNA stability of any coding sequence based on its codon composition and subsequently generate more stable (optimized) or unstable (deoptimized) variants encoding for the same protein. Further, we show that codon optimality predictions correlate with expression levels using fluorescent reporters and endogenous genes in human cells and zebrafish embryos. Therefore, iCodon will benefit basic biological research, as well as a wide range of applications for biotechnology and biomedicine.

scholarly journals A gain-of-function single nucleotide variant creates a new promoter which acts as an orientation-dependent enhancer-blocker

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yavor K. Bozhilov ◽  
Damien J. Downes ◽  
Jelena Telenius ◽  
A. Marieke Oudelaar ◽  
Emmanuel N. Olivier ◽  
...  
Keyword(s):  
Gene Expression ◽  
Genetic Diseases ◽  
Regulatory Elements ◽  
Base Change ◽  
Dependent Manner ◽  
Globin Genes ◽  
Single Nucleotide Variants ◽  
Single Nucleotide ◽  
Super Enhancer ◽  
Single Base Change

AbstractMany single nucleotide variants (SNVs) associated with human traits and genetic diseases are thought to alter the activity of existing regulatory elements. Some SNVs may also create entirely new regulatory elements which change gene expression, but the mechanism by which they do so is largely unknown. Here we show that a single base change in an otherwise unremarkable region of the human α-globin cluster creates an entirely new promoter and an associated unidirectional transcript. This SNV downregulates α-globin expression causing α-thalassaemia. Of note, the new promoter lying between the α-globin genes and their associated super-enhancer disrupts their interaction in an orientation-dependent manner. Together these observations show how both the order and orientation of the fundamental elements of the genome determine patterns of gene expression and support the concept that active genes may act to disrupt enhancer-promoter interactions in mammals as in Drosophila. Finally, these findings should prompt others to fully evaluate SNVs lying outside of known regulatory elements as causing changes in gene expression by creating new regulatory elements.

scholarly journals How the Avidity of Polymerase Binding to the -35/-10 Promoter Sites Affects Gene Expression

2019 ◽  
Author(s):  
Tal Einav ◽  
Rob Phillips
Keyword(s):  
Gene Expression ◽  
Rna Polymerase ◽  
Regulatory Elements ◽  
Physical Principle ◽  
Regulatory Sequences ◽  
Energy Matrix ◽  
Cellular Behavior ◽  
Inhibit Gene Expression ◽  
Small Set ◽  
Polymerase Binding

AbstractAlthough the key promoter elements necessary to drive transcription inEscherichia colihave long been understood, we still cannot predict the behavior of arbitrary novel promoters, hampering our ability to characterize the myriad of sequenced regulatory architectures as well as to design novel synthetic circuits. This work builds on a beautiful recent experiment by Urtechoet al.who measured the gene expression of over 10,000 promoters spanning all possible combinations of a small set of regulatory elements. Using this data, we demonstrate that a central claim in energy matrix models of gene expression – that each promoter element contributes independently and additively to gene expression – contradicts experimental measurements. We propose that a key missing ingredient from such models is the avidity between the -35 and -10 RNA polymerase binding sites and develop what we call arefined energy matrixmodel that incorporates this effect. We show that this the refined energy matrix model can characterize the full suite of gene expression data and explore several applications of this framework, namely, how multivalent binding at the -35 and -10 sites can buffer RNAP kinetics against mutations and how promoters that bind overly tightly to RNA polymerase can inhibit gene expression. The success of our approach suggests that avidity represents a key physical principle governing the interaction of RNA polymerase to its promoter.Significance StatementCellular behavior is ultimately governed by the genetic program encoded in its DNA and through the arsenal of molecular machines that actively transcribe its genes, yet we lack the ability to predict how an arbitrary DNA sequence will perform. To that end, we analyze the performance of over 10,000 regulatory sequences and develop a model that can predict the behavior of any sequence based on its composition. By considering promoters that only vary by one or two elements, we can characterize how different components interact, providing fundamental insights into the mechanisms of transcription.

scholarly journals Actively translated uORFs reduce translation and mRNA stability independent of NMD in Arabidopsis

2021 ◽  
Author(s):  
Hsin-Yen Larry Wu ◽  
Polly Yingshan Hsu
Keyword(s):  
Gene Expression ◽  
Mrna Stability ◽  
Gene Expression Regulation ◽  
Regulatory Elements ◽  
Expression Regulation ◽  
Ribosome Profiling ◽  
Translation Efficiency ◽  
Nonsense Mediated Decay ◽  
Protein Levels ◽  
Eukaryotic Genes

ABSTRACTUpstream ORFs (uORFs) are widespread cis-regulatory elements in the 5’ untranslated regions of eukaryotic genes. Translation of uORFs could negatively regulate protein synthesis by repressing main ORF (mORF) translation and by reducing mRNA stability presumably through nonsense-mediated decay (NMD). While the above expectations were supported in animals, they have not been extensively tested in plants. Using ribosome profiling, we systematically identified 2093 Actively Translated uORFs (ATuORFs) in Arabidopsis seedlings and examined their roles in gene expression regulation by integrating multiple genome-wide datasets. Compared with genes without uORFs, we found ATuORFs result in 38%, 14%, and 43% reductions in translation efficiency, mRNA stability, and protein levels, respectively. The effects of predicted but not actively translated uORFs are much weaker than those of ATuORFs. Interestingly, ATuORF-containing genes are also expressed at higher levels and encode longer proteins with conserved domains, features that are common in evolutionarily older genes. Moreover, we provide evidence that uORF translation in plants, unlike in vertebrates, generally does not trigger NMD. We found ATuORF-containing transcripts are degraded through 5’ to 3’ decay, while NMD targets are degraded through both 5’ to 3’ and 3’ to 5’ decay, suggesting uORF-associated mRNA decay and NMD have distinct genetic requirements. Furthermore, we showed ATuORFs and NMD repress translation through separate mechanisms. Our results reveal that the potent inhibition of uORFs on mORF translation and mRNA stability in plants are independent of NMD, highlighting a fundamental difference in gene expression regulation by uORFs in the plant and animal kingdoms.

scholarly journals Epigenomic landscape of enhancer elements during Hydra head organizer formation

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Puli Chandramouli Reddy ◽  
Akhila Gungi ◽  
Suyog Ubhe ◽  
Sanjeev Galande
Keyword(s):  
Gene Expression ◽  
Wnt Signaling ◽  
Histone Modifications ◽  
Specific Inhibitor ◽  
Regulatory Elements ◽  
The Body ◽  
Luciferase Reporter ◽  
Dependent Manner ◽  
Chromatin Architecture ◽  
Ectopic Activation

Abstract Background Axis patterning during development is accompanied by large-scale gene expression changes. These are brought about by changes in the histone modifications leading to dynamic alterations in chromatin architecture. The cis regulatory DNA elements also play an important role towards modulating gene expression in a context-dependent manner. Hydra belongs to the phylum Cnidaria where the first asymmetry in the body plan was observed and the oral-aboral axis originated. Wnt signaling has been shown to determine the head organizer function in the basal metazoan Hydra. Results To gain insights into the evolution of cis regulatory elements and associated chromatin signatures, we ectopically activated the Wnt signaling pathway in Hydra and monitored the genome-wide alterations in key histone modifications. Motif analysis of putative intergenic enhancer elements from Hydra revealed the conservation of bilaterian cis regulatory elements that play critical roles in development. Differentially regulated enhancer elements were identified upon ectopic activation of Wnt signaling and found to regulate many head organizer specific genes. Enhancer activity of many of the identified cis regulatory elements was confirmed by luciferase reporter assay. Quantitative chromatin immunoprecipitation analysis upon activation of Wnt signaling further confirmed the enrichment of H3K27ac on the enhancer elements of Hv_Wnt5a, Hv_Wnt11 and head organizer genes Hv_Bra1, CnGsc and Hv_Pitx1. Additionally, perturbation of the putative H3K27me3 eraser activity using a specific inhibitor affected the ectopic activation of Wnt signaling indicating the importance of the dynamic changes in the H3K27 modifications towards regulation of the genes involved in the head organizer activity. Conclusions The activation-associated histone marks H3K4me3, H3K27ac and H3K9ac mark chromatin in a similar manner as seen in bilaterians. We identified intergenic cis regulatory elements which harbor sites for key transcription factors involved in developmental processes. Differentially regulated enhancers exhibited motifs for many zinc-finger, T-box and ETS related TFs whose homologs have a head specific expression in Hydra and could be a part of the pioneer TF network in the patterning of the head. The ability to differentially modify the H3K27 residue is critical for the patterning of Hydra axis revealing a dynamic acetylation/methylation switch to regulate gene expression and chromatin architecture.

scholarly journals Regulation of c-jun gene expression in human T lymphocytes

Blood ◽  
1993 ◽  
Vol 81 (6) ◽  
pp. 1540-1548 ◽  
Author(s):  
D Chauhan ◽  
SM Kharbanda ◽  
E Rubin ◽  
BA Barut ◽  
A Mohrbacher ◽  
...  
Keyword(s):  
Gene Expression ◽  
T Cells ◽  
Messenger Rna ◽  
Jurkat Cells ◽  
Pokeweed Mitogen ◽  
Mrna Levels ◽  
Dependent Manner ◽  
B Cell Differentiation ◽  
Normal Peripheral Blood ◽  
Mrna Induction

Abstract The present studies have examined the effects of mitogens on induction of early response gene expression in normal peripheral blood T and Jurkat cells. Pokeweed mitogen (PWM) or anti-CD3 significantly increases c-jun messenger RNA (mRNA) levels in T cells. This transient PWM-related increase in c-jun transcripts is maximal after 15 to 30 minutes of exposure of T cells to PWM. PWM induces c-jun gene expression in a concentration-dependent manner. Moreover, PWM similarly induces expression of other genes coding for leucine zipper transcription factors, ie, jun-B and c-fos. Nuclear run on assays demonstrate that PWM treatment is associated with an increased rate of c-jun gene transcription. Transient expression assays with c-jun promoter fragments linked to the chloramphenicol acetyltransferase gene suggest that the PWM-induced increase in transcription is mediated by the AP-1 transcription factor complex. Moreover, treatment of T cells with actinomycin D to block further transcription before their culture with PWM suggests that the increase in c-jun gene expression by PWM is also regulated at least in part by a posttranscriptional mechanism. Cycloheximide does not alter c-jun mRNA induction by PWM. Finally, given that PWM induces B-cell differentiation in an interleukin-6 (IL- 6)-mediated, T-cell-dependent manner, the relationship of c-jun and IL- 6 gene expression in PWM-stimulated T cells was examined. The induction of IL-6 mRNA in T cells stimulated by PWM occurs after maximal induction of c-jun mRNA, at a time when the latter is no longer detectable. These findings suggest that PWM induces c-jun gene expression in T cells by a transcriptional and posttranscriptional mechanism and that AP-1 confers PWM inducibility of this gene. Because the IL-6 promoter has several potential transcriptional control elements, one of which is an AP-1-binding site, future experiments will evaluate the role of c-jun in the regulation of PWM-induced IL-6 synthesis by T cells.

Human glucagon gene promoter sequences regulating tissue-specific versus nutrient-regulated gene expression

2002 ◽  
Vol 282 (1) ◽  
pp. R173-R183 ◽  
Author(s):  
Min Nian ◽  
Jun Gu ◽  
David M. Irwin ◽  
Daniel J. Drucker
Keyword(s):  
Gene Expression ◽  
Gene Promoter ◽  
Regulatory Sequences ◽  
Dependent Manner ◽  
Specific Expression ◽  
Tissue Specific ◽  
High Fiber ◽  
Fiber Diet ◽  
Regulated Gene Expression

The glucagon-like peptides (GLPs) are synthesized and secreted in a nutrient-dependent manner in rodents; however, the factors regulating human GLP-1 and GLP-2 biosynthesis remain unclear. To understand how nutrients regulate human proglucagon gene expression, we studied the expression of a human proglucagon promoter-growth hormone (GH) transgene in 1.6 human glucagon-GH transgenic mice. Fasting-refeeding significantly decreased and increased the levels of circulating mouse insulin and transgene-derived hGH ( P < 0.05 fasting vs. refeeding) and decreased and upregulated, respectively, the levels of endogenous mouse proglucagon RNA in the ileum but not in the jejunum or colon. High-fiber feeding significantly increased the levels of glucose-stimulated circulating hGH and upregulated levels of mouse intestinal proglucagon gene expression in the jejunum, ileum, and colon ( P < 0.05, 0 vs. 30% fiber diet). In contrast, neither fasting-refeeding nor a high-fiber diet upregulated the expression of the human proglucagon promoter-hGH transgene. These findings demonstrate that human proglucagon gene regulatory sequences specifying tissue-specific expression in gut endocrine cells are not sufficient for recognition of energy-derived signals regulating murine glucagon gene expression in enteroendocrine cells in vivo.

scholarly journals Transposable elements as a potent source of diverse cis -regulatory sequences in mammalian genomes

2020 ◽  
Vol 375 (1795) ◽  
pp. 20190347 ◽  
Author(s):  
Vasavi Sundaram ◽  
Joanna Wysocka
Keyword(s):  
Gene Regulation ◽  
Transposable Elements ◽  
Regulatory Networks ◽  
Regulatory Elements ◽  
Regulatory Function ◽  
Specific Gene ◽  
Regulatory Sequences ◽  
Dependent Manner ◽  
Unique Contribution ◽  
Regulatory Potential

Eukaryotic gene regulation is mediated by cis -regulatory elements, which are embedded within the vast non-coding genomic space and recognized by the transcription factors in a sequence- and context-dependent manner. A large proportion of eukaryotic genomes, including at least half of the human genome, are composed of transposable elements (TEs), which in their ancestral form carried their own cis -regulatory sequences able to exploit the host trans environment to promote TE transcription and facilitate transposition. Although not all present-day TE copies have retained this regulatory function, the preexisting regulatory potential of TEs can provide a rich source of cis -regulatory innovation for the host. Here, we review recent evidence documenting diverse contributions of TE sequences to gene regulation by functioning as enhancers, promoters, silencers and boundary elements. We discuss how TE-derived enhancer sequences can rapidly facilitate changes in existing gene regulatory networks and mediate species- and cell-type-specific regulatory innovations, and we postulate a unique contribution of TEs to species-specific gene expression divergence in pluripotency and early embryogenesis. With advances in genome-wide technologies and analyses, systematic investigation of TEs' cis -regulatory potential is now possible and our understanding of the biological impact of genomic TEs is increasing. This article is part of a discussion meeting issue ‘Crossroads between transposons and gene regulation’.

Identification of a Gain-of-Function SNP Causing a New Model of α-Thalassaemia.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 523-523
Author(s):  
Marco De Gobbi ◽  
Vip Viprakasit ◽  
Pieter J. de Jong ◽  
Yuko Yoshinaga ◽  
Jan-Fang Cheng ◽  
...  
Keyword(s):  
Gene Expression ◽  
Binding Site ◽  
Globin Gene ◽  
Regulation Of Gene Expression ◽  
Histone H3 ◽  
Regulatory Elements ◽  
Causative Mutation ◽  
Regulatory Sequences ◽  
Chromosome 16 ◽  
Upstream Regulatory Sequences

Abstract The human α globin cluster includes an embryonic gene ζ and 2 fetal/adult genes (α2 and α1) arranged along the chromosome in the order in which they are expressed in development (5′-ζ-pseudoζ- αD- α2-α1-𝛉-3′). Fully activated expression of these genes in erythroid cells depends on upstream regulatory elements of which HS-40, located 40kb upstream of the cluster, appears to exert the greatest effect. We have recently shown that during terminal differentiation, key transcription factors (GATA-2, GATA-1, NF-E2, SCL complex) sequentially bind the α promoters and their regulatory elements and a domain of histone acetylation develops which eventually encompasses the entire α globin cluster including the upstream regulatory sequences. α-thalassemia most frequently results from deletions or point mutations affecting the structural α globin genes, but may also result from rare sporadic deletions which remove the upstream regulatory sequences. In a single family α globin expression was silenced by a mutation which drives an anti-sense RNA through the α gene. Alpha thalassemia may also result from inherited and acquired mutations in a trans-acting factor called ATRX. Over the past few years we have continued to screen for new mechanisms which lead to α thalassemia and thereby elucidate new principles underlying the regulation of gene expression in hemopoiesis. Here we describe a new mechanism of α thalassemia occurring in Pacific Islanders in whom we could detect no mutations or rearrangements in the α globin gene locus. Despite this, extensive genetic analysis showed unequivocally that the causative mutation is linked to the terminal 169kb of chromosome 16 (Viprakasit et al accompanying abstract). Analysis of globin synthesis, steady state RNA levels and detection of RNA in situ demonstrated that the mutation downregulates α globin transcription. To identify the mutation, we constructed a new BAC library from an affected homozygote, isolated and re-sequenced the candidate region and focussed further analysis on 8 SNPS within the α globin cluster, one of which creates a new GATA-1 binding site (GACA>GATA). Using primary erythroblasts from normal individuals and patients with this form of thalassemia, together with interspecific hybrids containing either the normal or abnormal copy of chromosome 16, we have shown that this SNP creates a new binding site in vivo for GATA-1 and the SCL complex. Furthermore, the chromatin at this site becomes activated as judged by acetylation of histone H3 and H4 (H3ac2 and H4ac4) and methylation of histone H3 (H3K4me2). Based on these data we postulate that an active transcriptional complex binding this new GATA site created by the SNP-mutation, could distract the upstream regulatory regions, which normally interact with the α globin promoter, and silence α globin gene expression. This model thus represents a new example of α globin gene down-regulation and a new mechanism by which gene expression can be perturbed during hemopoiesis.

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