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Gu X. d N/d S-H, a New Test to Distinguish Different Selection Modes in Protein Evolution and Cancer Evolution. J Mol Evol 2022; 90:342-351. [PMID: 35920867 DOI: 10.1007/s00239-022-10064-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2022] [Accepted: 06/14/2022] [Indexed: 11/25/2022]
Abstract
One of the most popular measures in the analysis of protein sequence evolution is the ratio of nonsynonymous distance (dN) to synonymous distance (dS). Under the assumption that synonymous substitutions in the coding region are selectively neutral, the dN/dS ratio can be used to statistically detect the adaptive evolution (or purifying selection) if dN/dS > 1 (or dN/dS < 1) significantly. However, due to strong structural constraints and/or variable functional constraints imposed on amino acid sites, most encoding genes in most species have demonstrated dN/dS < 1. Consequently, the statistical power for testing dN/dS = 1 may be insufficient to distinguish between different selection modes. In this paper, we propose a more powerful test, called dN/dS-H, in which a new parameter H, a relative measure of rate variation among sites, was introduced. Given the condition of strong purifying selections at some sites, the dN/dS-H model predicts dN/dS = 1-H for neutral evolution, dN/dS < 1-H for nearly neutral selection, and dN/dS > 1-H for adaptive evolution. The potential of this new method for resolving the neutral-adaptive debates is illustrated by the protein sequence evolution in vertebrates, Drosophila and yeasts, as well as somatic cancer evolution (specialized as the CN/CS-H test).
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Affiliation(s)
- Xun Gu
- The Laurence H. Baker Center in Bioinformatics on Biological Statistics, Iowa State University, Ames, IA, 50011, USA. .,Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA, 50011, USA. .,Program of Ecological and Evolutionary Biology, Iowa State University, Ames, IA, 50011, USA.
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A Genome-Wide Profiling of Glioma Patients with an IDH1 Mutation Using the Catalogue of Somatic Mutations in Cancer Database. Cancers (Basel) 2021; 13:cancers13174299. [PMID: 34503108 PMCID: PMC8428353 DOI: 10.3390/cancers13174299] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 08/20/2021] [Accepted: 08/21/2021] [Indexed: 02/08/2023] Open
Abstract
Simple Summary Glioma patients that present a somatic mutation in the isocitrate dehydrogenase 1 (IDH1) gene have a significantly better prognosis and overall survival than patients with the wild-type genotype. An IDH1 mutation is hypothesized to occur early during cellular transformation and leads to further genetic instability. A genome-wide profiling of glioma patients in the Catalogue of Somatic Mutations in Cancer (COSMIC) database was performed to classify the genetic differences in IDH1-mutant versus IDH1-wildtype patients. This classification will aid in a better understanding of how this specific mutation influences the genetic make-up of glioma and the resulting prognosis. Key differences in co-mutation and gene expression levels were identified that correlate with an improved prognosis. Abstract Gliomas are differentiated into two major disease subtypes, astrocytoma or oligodendroglioma, which are then characterized as either IDH (isocitrate dehydrogenase)-wild type or IDH-mutant due to the dramatic differences in prognosis and overall survival. Here, we investigated the genetic background of IDH1-mutant gliomas using the Catalogue of Somatic Mutations in Cancer (COSMIC) database. In astrocytoma patients, we found that IDH1 is often co-mutated with TP53, ATRX, AMBRA1, PREX1, and NOTCH1, but not CHEK2, EGFR, PTEN, or the zinc finger transcription factor ZNF429. The majority of the mutations observed in these genes were further confirmed to be either drivers or pathogenic by the Cancer-Related Analysis of Variants Toolkit (CRAVAT). Gene expression analysis showed down-regulation of DRG2 and MSN expression, both of which promote cell proliferation and invasion. There was also significant over-expression of genes such as NDRG3 and KCNB1 in IDH1-mutant astrocytoma patients. We conclude that IDH1-mutant glioma is characterized by significant genetic changes that could contribute to a better prognosis in glioma patients.
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Abstract
Mistranslation errors compromise fitness by wasting resources on nonfunctional proteins. In order to reduce the cost of mistranslations, natural selection chooses the most accurately translated codons at sites that are particularly important for protein structure and function. We investigated the determinants underlying selection for translational accuracy in several species of plants belonging to three clades: Brassicaceae, Fabidae, and Poaceae. Although signatures of translational selection were found in genes from a wide range of species, the underlying factors varied in nature and intensity. Indeed, the degree of synonymous codon bias at evolutionarily conserved sites varied among plant clades while remaining uniform within each clade. This is unlikely to solely reflect the diversity of tRNA pools because there is little correlation between synonymous codon bias and tRNA abundance, so other factors must affect codon choice and translational accuracy in plant genes. Accordingly, synonymous codon choice at a given site was affected not only by the selection pressure at that site, but also its participation in protein domains or mRNA secondary structures. Although these effects were detected in all the species we analyzed, their impact on translation accuracy was distinct in evolutionarily distant plant clades. The domain effect was found to enhance translational accuracy in dicot and monocot genes with a high GC content, but to oppose the selection of more accurate codons in monocot genes with a low GC content.
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Porceddu A, Zenoni S, Camiolo S. The signatures of selection for translational accuracy in plant genes. Genome Biol Evol 2013; 5:1117-26. [PMID: 23695187 PMCID: PMC3698923 DOI: 10.1093/gbe/evt078] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Little is known about the natural selection of synonymous codons within the coding sequences of plant genes. We analyzed the distribution of synonymous codons within plant coding sequences and found that preferred codons tend to encode the more conserved and functionally important residues of plant proteins. This was consistent among several synonymous codon families and applied to genes with different expression profiles and functions. Most of the randomly chosen alternative sets of codons scored weaker associations than the actual sets of preferred codons, suggesting that codon position within plant genes and codon usage bias have coevolved to maximize translational accuracy. All these findings are consistent with the mistranslation-induced protein misfolding theory, which predicts the natural selection of highly preferred codons more frequently at sites where translation errors could compromise protein folding or functionality. Our results will provide an important insight in future studies of protein folding, molecular evolution, and transgene design for optimal expression.
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Affiliation(s)
- Andrea Porceddu
- Dipartimento di Agraria, Sezione di Agronomia e Coltivazione Erbacee Genetica-SACEG, Università degli studi di Sassari, Italy.
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Shabalina SA, Spiridonov NA, Kashina A. Sounds of silence: synonymous nucleotides as a key to biological regulation and complexity. Nucleic Acids Res 2013; 41:2073-94. [PMID: 23293005 PMCID: PMC3575835 DOI: 10.1093/nar/gks1205] [Citation(s) in RCA: 187] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Messenger RNA is a key component of an intricate regulatory network of its own. It accommodates numerous nucleotide signals that overlap protein coding sequences and are responsible for multiple levels of regulation and generation of biological complexity. A wealth of structural and regulatory information, which mRNA carries in addition to the encoded amino acid sequence, raises the question of how these signals and overlapping codes are delineated along non-synonymous and synonymous positions in protein coding regions, especially in eukaryotes. Silent or synonymous codon positions, which do not determine amino acid sequences of the encoded proteins, define mRNA secondary structure and stability and affect the rate of translation, folding and post-translational modifications of nascent polypeptides. The RNA level selection is acting on synonymous sites in both prokaryotes and eukaryotes and is more common than previously thought. Selection pressure on the coding gene regions follows three-nucleotide periodic pattern of nucleotide base-pairing in mRNA, which is imposed by the genetic code. Synonymous positions of the coding regions have a higher level of hybridization potential relative to non-synonymous positions, and are multifunctional in their regulatory and structural roles. Recent experimental evidence and analysis of mRNA structure and interspecies conservation suggest that there is an evolutionary tradeoff between selective pressure acting at the RNA and protein levels. Here we provide a comprehensive overview of the studies that define the role of silent positions in regulating RNA structure and processing that exert downstream effects on proteins and their functions.
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Affiliation(s)
- Svetlana A Shabalina
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20984, USA.
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6
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Capes MD, DasSarma P, DasSarma S. The core and unique proteins of haloarchaea. BMC Genomics 2012; 13:39. [PMID: 22272718 PMCID: PMC3287961 DOI: 10.1186/1471-2164-13-39] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 01/24/2012] [Indexed: 11/10/2022] Open
Abstract
Background Since the first genome of a halophilic archaeon was sequenced in 2000, biologists have been advancing the understanding of genomic characteristics that allow for survival in the harsh natural environments of these organisms. An increase in protein acidity and GC-bias in the genome have been implicated as factors in tolerance to extreme salinity, desiccation, and high solar radiation. However, few previous attempts have been made to identify novel genes that would permit survival in such extreme conditions. Results With the recent release of several new complete haloarchaeal genome sequences, we have conducted a comprehensive comparative genomic analysis focusing on the identification of unique haloarchaeal conserved proteins that likely play key roles in environmental adaptation. Using bioinformatic methods, we have clustered 31,312 predicted proteins from nine haloarchaeal genomes into 4,455 haloarchaeal orthologous groups (HOGs). We assigned likely functions by association with established COG and KOG databases in NCBI. After identifying homologs in four additional haloarchaeal genomes, we determined that there were 784 core haloarchaeal protein clusters (cHOGs), of which 83 clusters were found primarily in haloarchaea. Further analysis found that 55 clusters were truly unique (tucHOGs) to haloarchaea and qualify as signature proteins while 28 were nearly unique (nucHOGs), the vast majority of which were coded for on the haloarchaeal chromosomes. Of the signature proteins, only one example with any predicted function, Ral, involved in desiccation/radiation tolerance in Halobacterium sp. NRC-1, was identified. Among the core clusters, 33% was predicted to function in metabolism, 25% in information transfer and storage, 10% in cell processes and signaling, and 22% belong to poorly characterized or general function groups. Conclusion Our studies have established conserved groups of nearly 800 protein clusters present in all haloarchaea, with a subset of 55 which are predicted to be accessory proteins that may be critical or essential for success in an extreme environment. These studies support core and signature genes and proteins as valuable concepts for understanding phylogenetic and phenotypic characteristics of coherent groups of organisms.
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Affiliation(s)
- Melinda D Capes
- Department of Microbiology and Immunology, Institute of Marine and Environmental Technology, University of Maryland, 701 East Pratt Street, Baltimore, MD 21202 USA
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Koonin EV, Wolf YI. Constraints and plasticity in genome and molecular-phenome evolution. Nat Rev Genet 2011; 11:487-98. [PMID: 20548290 DOI: 10.1038/nrg2810] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Multiple constraints variously affect different parts of the genomes of diverse life forms. The selective pressures that shape the evolution of viral, archaeal, bacterial and eukaryotic genomes differ markedly, even among relatively closely related animal and bacterial lineages; by contrast, constraints affecting protein evolution seem to be more universal. The constraints that shape the evolution of genomes and phenomes are complemented by the plasticity and robustness of genome architecture, expression and regulation. Taken together, these findings are starting to reveal complex networks of evolutionary processes that must be integrated to attain a new synthesis of evolutionary biology.
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Affiliation(s)
- Eugene V Koonin
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, Maryland 20894, USA.
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8
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Stoletzki N, Eyre-Walker A. The positive correlation between dN/dS and dS in mammals is due to runs of adjacent substitutions. Mol Biol Evol 2010; 28:1371-80. [PMID: 21115654 DOI: 10.1093/molbev/msq320] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
A positive correlation between ω, the ratio of the nonsynonymous and synonymous substitution rates, and dS, the synonymous substitution rate has recently been reported. This correlation is unexpected under simple evolutionary models. Here, we investigate two explanations for this correlation: first, whether it is a consequence of a statistical bias in the estimation of ω and second, whether it is due to substitutions at adjacent sites. Using simulations, we show that estimates of ω are biased when levels of divergence are low. This is true using the methods of Yang and Nielsen, Nei and Gojobori, and Muse and Gaut. Although the bias could generate a positive correlation between ω and dS, we show that it is unlikely to be the main determinant. Instead we show that the correlation is reduced when genes that are high quality in sequence, annotation, and alignment are used. The remaining--likely genuine--positive correlation appears to be due to adjacent tandem substitutions; single substitutions, though far more numerous, do not contribute to the correlation. Genuine adjacent substitutions may be due to mutation or selection.
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Affiliation(s)
- Nina Stoletzki
- Centre for Study of Evolution, School of Life Sciences, University of Sussex, Brighton, United Kingdom.
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Huang Y, Koonin EV, Lipman DJ, Przytycka TM. Selection for minimization of translational frameshifting errors as a factor in the evolution of codon usage. Nucleic Acids Res 2009; 37:6799-810. [PMID: 19745054 PMCID: PMC2777431 DOI: 10.1093/nar/gkp712] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In a wide range of genomes, it was observed that the usage of synonymous codons is biased toward specific codons and codon patterns. Factors that are implicated in the selection for codon usage include facilitation of fast and accurate translation. There are two types of translational errors: missense errors and processivity errors. There is considerable evidence in support of the hypothesis that codon usage is optimized to minimize missense errors. In contrast, little is known about the relationship between codon usage and frameshifting errors, an important form of processivity errors, which appear to occur at frequencies comparable to the frequencies of missense errors. Based on the recently proposed pause-and-slip model of frameshifting, we developed Frameshifting Robustness Score (FRS). We used this measure to test if the pattern of codon usage indicates optimization against frameshifting errors. We found that the FRS values of protein-coding sequences from four analyzed genomes (the bacteria Bacillus subtilis and Escherichia coli, and the yeasts Saccharomyces cerevisiae and Schizosaccharomyce pombe) were typically higher than expected by chance. Other properties of FRS patterns observed in B. subtilis, S. cerevisiae and S. pombe, such as the tendency of FRS to increase from the 5′- to 3′-end of protein-coding sequences, were also consistent with the hypothesis of optimization against frameshifting errors in translation. For E. coli, the results of different tests were less consistent, suggestive of a much weaker optimization, if any. Collectively, the results fit the concept of selection against mistranslation-induced protein misfolding being one of the factors shaping the evolution of both coding and non-coding sequences.
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Affiliation(s)
- Yang Huang
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, USA
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10
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Rocco L, Bencivenga S, Archimandritis A, Stingo V. Molecular characterization and chromosomal localization of spermatogenesis related sequences in Torpedo torpedo (Chondrichthyes, Torpediniformes). Mar Genomics 2009; 2:99-102. [DOI: 10.1016/j.margen.2009.06.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 05/26/2009] [Accepted: 06/03/2009] [Indexed: 10/20/2022]
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11
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Divergent patterns of selection on the DAB and DXB MHC class II loci in Xiphophorus fishes. Genetica 2008; 135:379-90. [DOI: 10.1007/s10709-008-9284-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2007] [Accepted: 06/09/2008] [Indexed: 10/21/2022]
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12
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Resch AM, Carmel L, Mariño-Ramírez L, Ogurtsov AY, Shabalina SA, Rogozin IB, Koonin EV. Widespread positive selection in synonymous sites of mammalian genes. Mol Biol Evol 2007; 24:1821-31. [PMID: 17522087 PMCID: PMC2632937 DOI: 10.1093/molbev/msm100] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Evolution of protein sequences is largely governed by purifying selection, with a small fraction of proteins evolving under positive selection. The evolution at synonymous positions in protein-coding genes is not nearly as well understood, with the extent and types of selection remaining, largely, unclear. A statistical test to identify purifying and positive selection at synonymous sites in protein-coding genes was developed. The method compares the rate of evolution at synonymous sites (Ks) to that in intron sequences of the same gene after sampling the aligned intron sequences to mimic the statistical properties of coding sequences. We detected purifying selection at synonymous sites in approximately 28% of the 1,562 analyzed orthologous genes from mouse and rat, and positive selection in approximately 12% of the genes. Thus, the fraction of genes with readily detectable positive selection at synonymous sites is much greater than the fraction of genes with comparable positive selection at nonsynonymous sites, i.e., at the level of the protein sequence. Unlike other genes, the genes with positive selection at synonymous sites showed no correlation between Ks and the rate of evolution in nonsynonymous sites (Ka), indicating that evolution of synonymous sites under positive selection is decoupled from protein evolution. The genes with purifying selection at synonymous sites showed significant anticorrelation between Ks and expression level and breadth, indicating that highly expressed genes evolve slowly. The genes with positive selection at synonymous sites showed the opposite trend, i.e., highly expressed genes had, on average, higher Ks. For the genes with positive selection at synonymous sites, a significantly lower mRNA stability is predicted compared to the genes with negative selection. Thus, mRNA destabilization could be an important factor driving positive selection in nonsynonymous sites, probably, through regulation of expression at the level of mRNA degradation and, possibly, also translation rate. So, unexpectedly, we found that positive selection at synonymous sites of mammalian genes is substantially more common than positive selection at the level of protein sequences. Positive selection at synonymous sites might act through mRNA destabilization affecting mRNA levels and translation.
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Affiliation(s)
- Alissa M Resch
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD, USA
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13
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Bierne N, Eyre-Walker A. Variation in synonymous codon use and DNA polymorphism within the Drosophila genome. J Evol Biol 2006; 19:1-11. [PMID: 16405571 DOI: 10.1111/j.1420-9101.2005.00996.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A strong negative correlation between the rate of amino-acid substitution and codon usage bias in Drosophila has been attributed to interference between positive selection at nonsynonymous sites and weak selection on codon usage. To further explore this possibility we have investigated polymorphism and divergence at three kinds of sites: synonymous, nonsynonymous and intronic in relation to codon bias in D. melanogaster and D. simulans. We confirmed that protein evolution is one of the main explicative parameters for interlocus codon bias variation (r(2) approximately 40%). However, intron or synonymous diversities, which could have been expected to be good indicators of local interference [here defined as the additional increase of drift due to selection on tightly linked sites, also called 'genetic draft' by Gillespie (2000)] did not covary significantly with codon bias or with protein evolution. Concurrently, levels of polymorphism were reduced in regions of low recombination rates whereas codon bias was not. Finally, while nonsynonymous diversities were very well correlated between species, neither synonymous nor intron diversities observed in D. melanogaster were correlated with those observed in D. simulans. All together, our results suggest that the selective constraint on the protein is a stable component of gene evolution while local interference is not. The pattern of variation in genetic draft along the genome therefore seems to be instable through evolutionary times and should therefore be considered as a minor determinant of codon bias variance. We argue that selective constraints for optimal codon usage are likely to be correlated with selective constraints on the protein, both between codons within a gene, as previously suggested, and also between genes within a genome.
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Affiliation(s)
- N Bierne
- Centre for the Study of Evolution and School of Biological Sciences, University of Sussex, Brighton, UK.
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14
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Rocha EPC. The quest for the universals of protein evolution. Trends Genet 2006; 22:412-6. [PMID: 16808987 DOI: 10.1016/j.tig.2006.06.004] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2006] [Revised: 04/07/2006] [Accepted: 06/05/2006] [Indexed: 11/16/2022]
Abstract
The sequences of proteins change at dramatically different rates. Unraveling the association between this variability and cellular and ecological processes will enable a better understanding of protein function and evolution. Although weak associations of protein evolutionary rates with a plethora of variables have been reported, none withstands comparison with the effect of expression levels. A recent report by Drummond et al. suggests that the dominant role of expression levels in slowing the rate of protein evolution stems from selection for translation robustness.
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Affiliation(s)
- Eduardo P C Rocha
- Unité Génomique des Génomes Bactériens, Institut Pasteur, 28 rue Dr Roux, 75015 Paris, France.
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15
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Jordan IK, Kondrashov FA, Rogozin IB, Tatusov RL, Wolf YI, Koonin EV. Constant relative rate of protein evolution and detection of functional diversification among bacterial, archaeal and eukaryotic proteins. Genome Biol 2001; 2:RESEARCH0053. [PMID: 11790256 PMCID: PMC64838 DOI: 10.1186/gb-2001-2-12-research0053] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2001] [Revised: 09/11/2001] [Accepted: 10/05/2001] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Detection of changes in a protein's evolutionary rate may reveal cases of change in that protein's function. We developed and implemented a simple relative rates test in an attempt to assess the rate constancy of protein evolution and to detect cases of functional diversification between orthologous proteins. The test was performed on clusters of orthologous protein sequences from complete bacterial genomes (Chlamydia trachomatis, C. muridarum and Chlamydophila pneumoniae), complete archaeal genomes (Pyrococcus horikoshii, P. abyssi and P. furiosus) and partially sequenced mammalian genomes (human, mouse and rat). RESULTS Amino-acid sequence evolution rates are significantly correlated on different branches of phylogenetic trees representing the great majority of analyzed orthologous protein sets from all three domains of life. However, approximately 1% of the proteins from each group of species deviates from this pattern and instead shows variation that is consistent with an acceleration of the rate of amino-acid substitution, which may be due to functional diversification. Most of the putative functionally diversified proteins from all three species groups are predicted to function at the periphery of the cells and mediate their interaction with the environment. CONCLUSIONS Relative rates of protein evolution are remarkably constant for the three species groups analyzed here. Deviations from this rate constancy are probably due to changes in selective constraints associated with diversification between orthologs. Functional diversification between orthologs is thought to be a relatively rare event. However, the resolution afforded by the test designed specifically for genomic-scale datasets allowed us to identify numerous cases of possible functional diversification between orthologous proteins.
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Affiliation(s)
- I K Jordan
- National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD20894, USA.
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16
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Alvarez-Valin F, Tort JF, Bernardi G. Nonrandom spatial distribution of synonymous substitutions in the GP63 gene from Leishmania. Genetics 2000; 155:1683-92. [PMID: 10924466 PMCID: PMC1461213 DOI: 10.1093/genetics/155.4.1683] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
In this work we analyze the variability in substitution rates in the GP63 gene from Leishmania. By using a sliding window to estimate substitution rates along the gene, we found that the rate of synonymous substitutions along the GP63 gene is highly correlated with both the rate of amino acid substitution and codon bias. Furthermore, we show that comparisons involving genes that represent independent phylogenetic lines yield very similar divergence/conservation patterns, thus suggesting that deterministic forces (i.e., nonstochastic forces such as selection) generated these patterns. We present evidence indicating that the variability in substitution rates is unambiguously related to functionally relevant features. In particular, there is a clear relationship between rates and the tertiary structure of the encoded protein since all divergent segments are located on the surface of the molecule and facing one side (almost parallel to the cell membrane) on the exposed surface of the organism. Remarkably, the protein segments encoded by these variable regions encircle the active site in a funnel-like distribution. These results strongly suggest that the pattern of nucleotide divergence and, notably, of synonymous divergence is affected by functional constraints.
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Affiliation(s)
- F Alvarez-Valin
- Sección Biomatemática, Facultad de Ciencias, Montevideo 11400, Uruguay.
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17
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Wagner A. Decoupled evolution of coding region and mRNA expression patterns after gene duplication: implications for the neutralist-selectionist debate. Proc Natl Acad Sci U S A 2000; 97:6579-84. [PMID: 10823904 PMCID: PMC18666 DOI: 10.1073/pnas.110147097] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The neutralist perspective on molecular evolution maintains that the vast majority of mutations affecting gene function are neutral or deleterious. After a gene duplication where both genes are retained, it predicts that original and duplicate genes diverge at clock-like rates. This prediction is usually tested for coding sequences, but can also be applied to another important aspect of gene function, the genes' expression pattern. Moreover, if both sequence and expression pattern diverge at clock-like rates, a correlation between divergence in sequence and divergence in expression patterns is expected. Duplicate gene pairs with more highly diverged sequences should also show more highly diverged expression patterns. This prediction is tested for a large sample of duplicated genes in the yeast Saccharomyces cerevisiae, using both genome sequence and microarray expression data. Only a weak correlation is observed, suggesting that coding sequence and mRNA expression patterns of duplicate gene pairs evolve independently and at vastly different rates. Implications of this finding for the neutralist-selectionist debate are discussed.
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Affiliation(s)
- A Wagner
- The Santa Fe Institute, University of New Mexico, Department of Biology, 167A Castetter Hall, Albuquerque, NM 87131-1091, USA.
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18
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Abstract
Evolution occurs through genome variation followed by selection. Because DNA sequence context affects the activity of enzymes that copy, move and repair DNA, there are intrinsic variations in the probability of genetic variation along a genome. These intrinsic variations can be affected by selective pressure. Codon changes that do not alter the encoded amino acids may still have effects on the local rate of sequence change. Large gene families could encode a successful genetic framework by which to evolve new, functional members. The speed of adaptation to environmental challenges may be improved when the distinct mechanisms of genetic change come under regulatory control. Natural selection operates on mechanisms that generate and modulate diversity as it does on all biological functions.
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Smith NG, Hurst LD. The effect of tandem substitutions on the correlation between synonymous and nonsynonymous rates in rodents. Genetics 1999; 153:1395-402. [PMID: 10545467 PMCID: PMC1460828 DOI: 10.1093/genetics/153.3.1395] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Nonsynonymous substitutions in DNA cause amino acid substitutions while synonymous substitutions in DNA leave amino acids unchanged. The cause of the correlation between the substitution rates at nonsynonymous (K(A)) and synonymous (K(S)) sites in mammals is a contentious issue, and one that impacts on many aspects of molecular evolution. Here we use a large set of orthologous mammalian genes to investigate the causes of the K(A)-K(S) correlation in rodents. The strength of the K(A)-K(S) correlation exceeds the neutral theory expectation when substitution rates are estimated using algorithmic methods, but not when substitution rates are estimated by maximum likelihood. Irrespective of this methodological uncertainty the strength of the K(A)-K(S) correlation appears mostly due to tandem substitutions, an excess of which is generated by substitutional nonindependence. Doublet mutations cannot explain the excess of tandem synonymous-nonsynonymous substitutions, and substitution patterns indicate that selection on silent sites is the likely cause. We find no evidence for selection on codon usage. The nature of the relationship between synonymous divergence and base composition is unclear because we find a significant correlation if we use maximum-likelihood methods but not if we use algorithmic methods. Finally, we find that K(S) is reduced at the start of genes, which suggests that selection for RNA structure may affect silent sites in mammalian protein-coding genes.
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Affiliation(s)
- N G Smith
- Department of Biology and Biochemistry, University of Bath, Bath B42 7AY, United Kingdom.
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20
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Chiusano ML, D'Onofrio G, Alvarez-Valin F, Jabbari K, Colonna G, Bernardi G. Correlations of nucleotide substitution rates and base composition of mammalian coding sequences with protein structure. Gene 1999; 238:23-31. [PMID: 10570980 DOI: 10.1016/s0378-1119(99)00258-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
We investigated the relationships between the nucleotide substitution rates and the predicted secondary structures in the three states representation (alpha-helix, beta-sheet, and coil). The analysis was carried out on 34 alignments, each of which comprised sequences belonging to at least four different mammalian orders. The rates of synonymous substitution were found to be significantly different in regions predicted to be alpha-helix, beta-sheet, or coil. Likewise, the nonsynonymous rates also differ, although expectedly at a lower extent, in the three types of secondary structure, suggesting that different selective constraints associated with the different structures are affecting in a similar way the synonymous and nonsynonymous rates. Moreover, the base composition of the third codon positions is different in coding sequence regions corresponding to different secondary structures of proteins.
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Affiliation(s)
- M L Chiusano
- Laboratorio di Evoluzione Molecolare, Stazione Zoologica Anton Dohrn, Naples, Italy
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21
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Abstract
Most descriptions of mutation have emphasized its negative consequences, and randomness with respect to biological function. This book seeks to balance the discussion by emphasizing mechanisms that both diversify the genome and increase the probability that a genome's descendants will survive. This chapter provides a framework for, and overview of, the diverse contributions to this book; these contributions will be stimulating companions, well into the 21st Century, as we work to comprehend the information contained in genomic databases. Genomes that encode "better" amino acid sequences are at a selective advantage. Genomes that generate diversity also are at an advantage to the extent that they can navigate efficiently through the space of possible sequence changes. Biochemical systems that tend to increase the ratio of useful to destructive genetic change may harness preexisting information (horizontal gene transfer, DNA translocation and/or DNA duplication), focus the location, timing, and extent of genetic change, adjust the dynamic range of a gene's activity, and/or sample regulatory connections between sites distributed across the genome. Rejecting entirely random genetic variation as the substrate of genome evolution is not a refutation, but rather provides a deeper understanding, of the theory of natural selection of Darwin and Wallace. The fittest molecular strategies survive, along with descendants of the genomes that encode them.
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22
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Comeron JM, Kreitman M. The correlation between synonymous and nonsynonymous substitutions in Drosophila: mutation, selection or relaxed constraints? Genetics 1998; 150:767-75. [PMID: 9755207 PMCID: PMC1460343 DOI: 10.1093/genetics/150.2.767] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Codon usage bias, the preferential use of particular codons within each codon family, is characteristic of synonymous base composition in many species, including Drosophila, yeast, and many bacteria. Preferential usage of particular codons in these species is maintained by natural selection acting largely at the level of translation. In Drosophila, as in bacteria, the rate of synonymous substitution per site is negatively correlated with the degree of codon usage bias, indicating stronger selection on codon usage in genes with high codon bias than in genes with low codon bias. Surprisingly, in these organisms, as well as in mammals, the rate of synonymous substitution is also positively correlated with the rate of nonsynonymous substitution. To investigate this correlation, we carried out a phylogenetic analysis of substitutions in 22 genes between two species of Drosophila, Drosophila pseudoobscura and D. subobscura, in codons that differ by one replacement and one synonymous change. We provide evidence for a relative excess of double substitutions in the same species lineage that cannot be explained by the simultaneous mutation of two adjacent bases. The synonymous changes in these codons also cannot be explained by a shift to a more preferred codon following a replacement substitution. We, therefore, interpret the excess of double codon substitutions within a lineage as being the result of relaxed constraints on both kinds of substitutions in particular codons.
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Affiliation(s)
- J M Comeron
- Department of Ecology and Evolution, University of Chicago, Chicago, Illinois 60637, USA.
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23
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Porter TD. Correlation between codon usage, regional genomic nucleotide composition, and amino acid composition in the cytochrome P-450 gene superfamily. BIOCHIMICA ET BIOPHYSICA ACTA 1995; 1261:394-400. [PMID: 7742368 DOI: 10.1016/0167-4781(95)00037-h] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The codon usage bias of 110 mammalian cytochrome P-450 genes has been determined and analyzed in relation to a variety of genetic, biochemical, and physiological parameters. In those P-450 genes exhibiting biased usage the preferred codons generally do not differ among the four species examined (rat, rabbit, man, and mouse) or from the predominantly used codons identified for all sequenced genes in a recent data base analysis (Wada et al. (1992) Nucleic Acids Res. 20 (Suppl.), 2111-2118). Codon usage bias does not correlate with evolutionary relationships, evolutionary age, or with the extent of evolutionary conservation of orthologous proteins; there is no obvious correlation with the level of expression of a given P-450, with its inducibility, nor with its physiologic role; and neither the preferred codons nor the degree of bias differ for P-450s expressed in different tissues. Codon usage bias does correlate with the C+G content at the codon third position, and thus preferred codons usually end in C or G; for those P-450s for which gene sequences are available this bias also correlates with the C + G content of the intronic and flanking regions of these genes. Moreover, a lesser increase in the C + G content at the codon first and second positions is also evident in genes located in regions of high C + G content; this leads to predictable differences in the amino acid compositions of P-450 enzymes that correlate with genomic nucleotide composition and the degree of bias in codon usage.
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Affiliation(s)
- T D Porter
- Division of Pharmacology and Experimental Therapeutics, College of Pharmacy, University of Kentucky, Lexington 40536-0082, USA
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24
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Mouchiroud D, Gautier C, Bernardi G. Frequencies of synonymous substitutions in mammals are gene-specific and correlated with frequencies of nonsynonymous substitutions. J Mol Evol 1995; 40:107-13. [PMID: 7714909 DOI: 10.1007/bf00166602] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The frequencies of synonymous substitutions of mammalian genes cover a much wider range than previously thought. We report here that the different frequencies found in homologous genes from a given mammalian pair are correlated with those in the same homologous genes from a different mammalian pair. This indicates that the frequencies of synonymous substitutions are gene-specific (as are the frequencies of nonsynonymous substitutions), or, in other words, that "fast" and "slow" genes in one mammal are fast and slow, respectively, in any other one. Moreover, the frequencies of synonymous substitutions are correlated with the frequencies of nonsynonymous substitution in the same genes.
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Affiliation(s)
- D Mouchiroud
- Laboratoire de Biométrie, Génétique et Biologie des Populations, U.R.A. 243, Université Claude Bernard, Villeurbanne, France
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25
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Wolfe KH, Sharp PM. Mammalian gene evolution: nucleotide sequence divergence between mouse and rat. J Mol Evol 1993; 37:441-56. [PMID: 8308912 DOI: 10.1007/bf00178874] [Citation(s) in RCA: 147] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
As a paradigm of mammalian gene evolution, the nature and extent of DNA sequence divergence between homologous protein-coding genes from mouse and rat have been investigated. The data set examined includes 363 genes totalling 411 kilobases, making this by far the largest comparison conducted between a single pair of species. Mouse and rat genes are on average 93.4% identical in nucleotide sequence and 93.9% identical in amino acid sequence. Individual genes vary substantially in the extent of nonsynonymous nucleotide substitution, as expected from protein evolution studies; here the variation is characterized. The extent of synonymous (or silent) substitution also varies considerably among genes, though the coefficient of variation is about four times smaller than for nonsynonymous substitutions. A small number of genes mapped to the X-chromosome have a slower rate of molecular evolution than average, as predicted if molecular evolution is "male-driven." Base composition at silent sites varies from 33% to 95% G+C in different genes; mouse and rat homologues differ on average by only 1.7% in silent-site G+C, but it is shown that this is not necessarily due to any selective constraint on their base composition. Synonymous substitution rates and silent site base composition appear to be related (genes at intermediate G+C have on average higher rates), but the relationship is not as strong as in our earlier analyses. Rates of synonymous and nonsynonymous substitution are correlated, apparently because of an excess of substitutions involving adjacent pairs of nucleotides. Several factors suggest that synonymous codon usage in rodent genes is not subject to selection.
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Affiliation(s)
- K H Wolfe
- Department of Genetics, University of Dublin, Trinity College, Ireland
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26
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Abstract
A new statistical test has been developed to detect selection on silent sites. This test compares the codon usage within a gene and thus does not require knowledge of which genes are under the greatest selection, that there exist common trends in codon usage across genes, or that genes have the same mutation pattern. It also controls for mutational biases that might be introduced by the adjacent bases. The test was applied to 62 mammalian sequences, and significant codon usage biases were detected in all three species examined (humans, rats, and mice). However, these biases appear not to be the consequence of selection, but of the first base pair in the codon influencing the mutation pattern at the third position.
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Affiliation(s)
- A C Eyre-Walker
- Institute of Cell, Animal and Population Biology, University of Edinburgh, United Kingdom
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27
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Sharp PM. Determinants of DNA sequence divergence between Escherichia coli and Salmonella typhimurium: codon usage, map position, and concerted evolution. J Mol Evol 1991; 33:23-33. [PMID: 1909371 DOI: 10.1007/bf02100192] [Citation(s) in RCA: 171] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The nature and extent of DNA sequence divergence between homologous protein-coding genes from Escherichia coli and Salmonella typhimurium have been examined. The degree of divergence varies greatly among genes at both synonymous (silent) and nonsynonymous sites. Much of the variation in silent substitution rates can be explained by natural selection on synonymous codon usage, varying in intensity with gene expression level. Silent substitution rates also vary significantly with chromosomal location, with genes near oriC having lower divergence. Certain genes have been examined in more detail. In particular, the duplicate genes encoding elongation factor Tu, tufA and tufB, from S. typhimurium have been compared to their E. coli homologues. As expected these very highly expressed genes have high codon usage bias and have diverged very little between the two species. Interestingly, these genes, which are widely spaced on the bacterial chromosome, also appear to be undergoing concerted evolution, i.e., there has been exchange between the loci subsequent to the divergence of the two species.
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Affiliation(s)
- P M Sharp
- Department of Genetics, Trinity College, Dublin, Ireland
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28
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Abstract
I briefly discuss some aspects of theoretical molecular biology. Specifically, I include the issues of searches for homologies via string matchings, for patterns of specific nucleotide groupings and of sequence-structure relationship. The various approaches developed in order to achieve this end are described, attempting to convey some of the excitement in this quickly growing field.
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Affiliation(s)
- R Nussinov
- Sackler Institute of Molecular Medicine, Sackler Faculty of Medicine, Tel Aviv Univrsity, Ramat Aviv, Israel
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29
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Abstract
Observed patterns of synonymous codon usage are explained in terms of the joint effects of mutation, selection, and random drift. Examination of the codon usage in 165 Escherichia coli genes reveals a consistent trend of increasing bias with increasing gene expression level. Selection on codon usage appears to be unidirectional, so that the pattern seen in lowly expressed genes is best explained in terms of an absence of strong selection. A measure of directional synonymous-codon usage bias, the Codon Adaptation Index, has been developed. In enterobacteria, rates of synonymous substitution are seen to vary greatly among genes, and genes with a high codon bias evolve more slowly. A theoretical study shows that the patterns of extreme codon bias observed for some E. coli (and yeast) genes can be generated by rather small selective differences. The relative plausibilities of various theoretical models for explaining nonrandom codon usage are discussed.
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30
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Porter TD, Beck TW, Kasper CB. Complementary DNA and amino acid sequence of rat liver microsomal, xenobiotic epoxide hydrolase. Arch Biochem Biophys 1986; 248:121-9. [PMID: 3755318 DOI: 10.1016/0003-9861(86)90408-x] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The coding nucleotide sequence for rat liver microsomal, xenobiotic epoxide hydrolase was determined from two overlapping cDNA clones, which together contain 1750 nucleotides complementary to epoxide hydrolase mRNA. The single open reading frame of 1365 nucleotides codes for a 455 amino acid polypeptide with a molecular weight of 52,581. The deduced amino acid composition agrees well with those determined by direct amino acid analysis of the rat protein, and the amino acid sequence is 81% identical to that of rabbit epoxide hydrolase. Analysis of codon usage for epoxide hydrolase, and that of rabbit epoxide hydrolase. Analysis of codon usage for epoxide hydrolase, and comparison to codon usage for NADPH-cytochrome P-450 oxidoreductase and cytochromes P-450b, P-450d, and P-450PCN, suggest that epoxide hydrolase is more conserved than cytochromes P-450b and P-450PCN; comparison of the extent of sequence conservation for 12 homologous proteins between the rat and rabbit, including cytochrome P-450b, supports this hypothesis, and indicates that much of epoxide hydrolase is constrained to maintain its hydrophobic character, consistent with its intramembranous location. The predicted membrane topology of epoxide hydrolase delineates 6 membrane-spanning segments, less than the 8 or 10 predicted for two cytochrome P-450 isozymes; the lower number of membrane-spanning segments predicted for epoxide hydrolase correlates with its lesser dependence on the membrane for maintenance of its tertiary structure and catalytic activity.
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