Selection, adaptation, and bacterial operons

Genome ◽  
1989 ◽  
Vol 31 (1) ◽  
pp. 265-271 ◽  
Author(s):  
Barry G. Hall
Keyword(s):  
Structural Gene ◽  
Point Mutations ◽  
Gene Mutations ◽  
Adaptive Mutation ◽  
Evolutionary Potential ◽  
Adaptive Mutations ◽  
Metabolic Functions ◽  
Metabolic Capability ◽  
Regulatory Mutations ◽  
Selection For

Bacteria are especially useful as systems to study the molecular basis of adaptive evolution. Selection for novel metabolic capabilities has allowed us to study the evolutionary potential of organisms and has shown that there are three major "strategies" for the evolution of new metabolic functions. (i) Regulatory mutations may allow a gene to be expressed under unusual conditions. If the product ofthat gene is already active toward a novel resource, then a regulatory mutation alone may confer a new metabolic capability. (ii) Structural gene mutations may alter the catalytic properties of enzymes so that they can act on novel substrates. These structural gene mutations may dramatically improve catalytic capabilities, and in some cases they can confer entirely new capabilities upon enzymes. In most cases both regulatory and structural gene mutations are required for the effective evolution of new metabolic functions. (iii) Operons that are normally silent, or cryptic, may be activated by either point mutations or by the action of mobile genetic elements. When activated, these operons can provide entirely new pathways for the metabolism of novel resources. Selection can also play a role in modulating the probability that a particular adaptive mutation will occur. In this paper I present evidence that a specific adaptive mutation, reversion of the metB1 mutation, occurs 60 to 80 times more frequently during prolonged selection on plates under conditions where the members of the population are not growing than it does in growing cells under nonselective conditions. This selective condition, methionine starvation, does not increase the frequency of other mutations unrelated to methionine biosynthesis. Thus, contrary to our present notions, selection can act not only to reveal preexisting mutations but to modulate the frequency with which adaptive mutations occur.Key words: mutation rates, molecular evolution, adaptive mutations, cryptic genes.

scholarly journals Molecular Basis of In Vivo Resistance to Sulfadoxine-Pyrimethamine in African Adult Patients Infected withPlasmodium falciparum Malaria Parasites

1998 ◽  
Vol 42 (7) ◽  
pp. 1811-1814 ◽  
Author(s):  
Leonardo K. Basco ◽  
Rachida Tahar ◽  
Pascal Ringwald
Keyword(s):  
Dihydrofolate Reductase ◽  
Point Mutations ◽  
Gene Mutations ◽  
Adult Patients ◽  
Wild Type ◽  
Dihydropteroate Synthase ◽  
Reductase Gene ◽  
Parasite Populations

ABSTRACT In vitro sulfadoxine and pyrimethamine resistance has been associated with point mutations in the dihydropteroate synthase and dihydrofolate reductase domains, respectively, but the in vivo relevance of these point mutations has not been well established. To analyze the correlation between genotype and phenotype, 10 Cameroonian adult patients were treated with sulfadoxine-pyrimethamine and followed up for 28 days. After losses to follow-up (n = 1) or elimination of DNA samples due to mixed parasite populations with pyrimethamine-sensitive and pyrimethamine-resistant profiles (n = 3), parasite genomic DNA from day 0 blood samples of six patients were analyzed by DNA sequencing. Three patients who were cured had isolates characterized by a wild-type or mutant dihydrofolate reductase gene (with one or two mutations) and a wild-type dihydropteroate synthase gene. Three other patients who failed to respond to sulfadoxine-pyrimethamine treatment carried isolates with triple dihydrofolate reductase gene mutations and either a wild-type or a mutant dihydropteroate synthase gene. Three dihydrofolate reductase gene codons (51, 59, and 108) may be reliable genetic markers that can accurately predict the clinical outcome of sulfadoxine-pyrimethamine treatment in Africa.

scholarly journals A Single Adaptive Mutation in Sodium Taurocholate Cotransporting Polypeptide Induced by Hepadnaviruses Determines Virus Species Specificity

2018 ◽  
Vol 93 (5) ◽  
Author(s):  
Junko S. Takeuchi ◽  
Kento Fukano ◽  
Masashi Iwamoto ◽  
Senko Tsukuda ◽  
Ryosuke Suzuki ◽  
...  
Keyword(s):  
Amino Acid ◽  
Virus Infection ◽  
Positive Selection ◽  
Sodium Taurocholate ◽  
Arms Race ◽  
Adaptive Mutation ◽  
Molecular Evidence ◽  
Adaptive Mutations ◽  
Wide Range ◽  
Coevolutionary Arms Race

ABSTRACTHepatitis B virus (HBV) and its hepadnavirus relatives infect a wide range of vertebrates, from fish to human. Hepadnaviruses and their hosts have a long history of acquiring adaptive mutations. However, there are no reports providing direct molecular evidence for such a coevolutionary “arms race” between hepadnaviruses and their hosts. Here, we present evidence suggesting that the adaptive evolution of the sodium taurocholate cotransporting polypeptide (NTCP), an HBV receptor, has been influenced by virus infection. Evolutionary analysis of the NTCP-encoding genes from 20 mammals showed that most NTCP residues are highly conserved among species, exhibiting evolution under negative selection (dN/dSratio [ratio of nonsynonymous to synonymous evolutionary changes] of <1); this observation implies that the evolution of NTCP is restricted by maintaining its original protein function. However, 0.7% of NTCP amino acid residues exhibit rapid evolution under positive selection (dN/dSratio of >1). Notably, a substitution at amino acid (aa) 158, a positively selected residue, converting the human NTCP to a monkey-type sequence abrogated the capacity to support HBV infection; conversely, a substitution at this residue converting the monkey Ntcp to the human sequence was sufficient to confer HBV susceptibility. Together, these observations suggested a close association of the aa 158 positive selection with the pressure by virus infection. Moreover, the aa 158 sequence determined attachment of the HBV envelope protein to the host cell, demonstrating the mechanism whereby HBV infection would create positive selection at this NTCP residue. In summary, we provide the first evidence in agreement with the function of hepadnavirus as a driver for inducing adaptive mutation in host receptor.IMPORTANCEHBV and its hepadnavirus relatives infect a wide range of vertebrates, with a long infectious history (hundreds of millions of years). Such a long history generally allows adaptive mutations in hosts to escape from infection while simultaneously allowing adaptive mutations in viruses to overcome host barriers. However, there is no published molecular evidence for such a coevolutionary arms race between hepadnaviruses and hosts. In the present study, we performed coevolutionary phylogenetic analysis between hepadnaviruses and the sodium taurocholate cotransporting polypeptide (NTCP), an HBV receptor, combined with virological experimental assays for investigating the biological significance of NTCP sequence variation. Our data provide the first molecular evidence supporting that HBV-related hepadnaviruses drive adaptive evolution in the NTCP sequence, including a mechanistic explanation of how NTCP mutations determine host viral susceptibility. Our novel insights enhance our understanding of how hepadnaviruses evolved with their hosts, permitting the acquisition of strong species specificity.

scholarly journals More effective drugs lead to harder selective sweeps in the evolution of drug resistance in HIV-1

eLife ◽  
2016 ◽  
Vol 5 ◽  
Author(s):  
Alison F Feder ◽  
Soo-Yon Rhee ◽  
Susan P Holmes ◽  
Robert W Shafer ◽  
Dmitri A Petrov ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Hiv Treatment ◽  
Adaptive Mutation ◽  
Selective Sweeps ◽  
Resistance Mutations ◽  
Consensus Sequences ◽  
Adaptive Mutations ◽  
Slow Evolution ◽  
Effective Drugs ◽  
Hiv 1

In the early days of HIV treatment, drug resistance occurred rapidly and predictably in all patients, but under modern treatments, resistance arises slowly, if at all. The probability of resistance should be controlled by the rate of generation of resistance mutations. If many adaptive mutations arise simultaneously, then adaptation proceeds by soft selective sweeps in which multiple adaptive mutations spread concomitantly, but if adaptive mutations occur rarely in the population, then a single adaptive mutation should spread alone in a hard selective sweep. Here, we use 6717 HIV-1 consensus sequences from patients treated with first-line therapies between 1989 and 2013 to confirm that the transition from fast to slow evolution of drug resistance was indeed accompanied with the expected transition from soft to hard selective sweeps. This suggests more generally that evolution proceeds via hard sweeps if resistance is unlikely and via soft sweeps if it is likely.

scholarly journals The Wiskott-Aldrich syndrome and X-linked congenital thrombocytopenia are caused by mutations of the same gene

Blood ◽  
1995 ◽  
Vol 86 (10) ◽  
pp. 3797-3804 ◽  
Author(s):  
Q Zhu ◽  
M Zhang ◽  
RM Blaese ◽  
JM Derry ◽  
A Junker ◽  
...  
Keyword(s):  
Clinical Symptoms ◽  
Point Mutations ◽  
Gene Mutations ◽  
Exon Skipping ◽  
Splice Site Mutation ◽  
Missense Mutations ◽  
Site Mutation ◽  
Exon 2 ◽  
Wiskott Aldrich Syndrome ◽  
Was Gene

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder characterized by thrombocytopenia, small platelets, eczema, recurrent infections, and immunodeficiency. Besides the classic WAS phenotype, there is a group of patients with congenital X-linked thrombocytopenia (XLT) who have small platelets but only transient eczema, if any, and minimal immune deficiency. Because the gene responsible for WAS has been sequenced, it was possible to correlate the WAS phenotypes with WAS gene mutations. Using a fingerprinting screening technique, we determined the approximate location of the mutation in 13 unrelated WAS patients with mild to severe clinical symptoms. Direct sequence analysis of cDNA and genomic DNA obtained from patient-derived cell lines showed 12 unique mutations distributed throughout the WAS gene, including insertions, deletions, and point mutations resulting in amino acid substitutions, termination, exon skipping, or splicing defects. Of 4 unrelated patients with the XLT phenotype, 3 had missense mutations affecting exon 2 and 1 had a splice-site mutation affecting exon 9. Patients with classic WAS had more complex mutations, resulting in termination codons, frameshift, and early termination. These findings provide direct evidence that XLT and WAS are caused by mutations of the same gene and suggest that severe clinical phenotypes are associated with complex mutations.

scholarly journals Genetic diseases of the Kennedy pathways for membrane synthesis

2020 ◽  
Vol 295 (51) ◽  
pp. 17877-17886
Author(s):  
Mahtab Tavasoli ◽  
Sarah Lahire ◽  
Taryn Reid ◽  
Maren Brodovsky ◽  
Christopher R. McMaster
Keyword(s):  
Single Gene ◽  
Genetic Diseases ◽  
Point Mutations ◽  
Gene Mutations ◽  
Hereditary Diseases ◽  
Biological Functions ◽  
Phospholipid Synthesis ◽  
Spastic Paraplegia ◽  
Kennedy Pathway ◽  
Single Gene Disorders

The two branches of the Kennedy pathways (CDP-choline and CDP-ethanolamine) are the predominant pathways responsible for the synthesis of the most abundant phospholipids, phosphatidylcholine and phosphatidylethanolamine, respectively, in mammalian membranes. Recently, hereditary diseases associated with single gene mutations in the Kennedy pathways have been identified. Interestingly, genetic diseases within the same pathway vary greatly, ranging from muscular dystrophy to spastic paraplegia to a childhood blinding disorder to bone deformations. Indeed, different point mutations in the same gene (PCYT1; CCTα) result in at least three distinct diseases. In this review, we will summarize and review the genetic diseases associated with mutations in genes of the Kennedy pathway for phospholipid synthesis. These single-gene disorders provide insight, indeed direct genotype-phenotype relationships, into the biological functions of specific enzymes of the Kennedy pathway. We discuss potential mechanisms of how mutations within the same pathway can cause disparate disease.

scholarly journals Solid-Phase Amplification for Detection of C282Y and H63D Hemochromatosis (HFE) Gene Mutations

2001 ◽  
Vol 47 (8) ◽  
pp. 1384-1389 ◽  
Author(s):  
Mark S Turner ◽  
Sarah Penning ◽  
Angela Sharp ◽  
Valentine J Hyland ◽  
Ray Harris ◽  
...  
Keyword(s):  
Solid Phase ◽  
Point Mutations ◽  
Gene Mutations ◽  
Pcr Primers ◽  
Clinical Samples ◽  
Hfe Gene ◽  
Target Sequence ◽  
Nucleotide Polymorphisms ◽  
Nitrophenyl Phosphate ◽  
Hemochromatosis Gene

Abstract Background: There is a need for simple, rapid, and inexpensive methods for the detection of single-nucleotide polymorphisms. Our aim was to develop a single-tube ELISA-like PCR assay and evaluate it by detecting the common C282Y and H63D mutations found in the hemochromatosis gene (HFE) by use of clinical samples. Methods: The method, termed solid-phase amplification (SPA), involves dual liquid- and solid-phase amplification of a target sequence by the use of two PCR primers, one of which is in two forms: the first is covalently immobilized to the wall of a microwell, and the second is free in solution. During allele-specific amplification, both the free and solid-phase amplicons are labeled by incorporation of digoxigenin (DIG)-dUTP. The amount of surface-bound amplicon is determined colorimetrically by the use of an alkaline phosphatase-anti-DIG-Fab conjugate and p-nitrophenyl phosphate. Results: Two different amplicon-labeling methods were evaluated. Analysis of 173 clinical samples for the C282Y and H63D HFE point mutations with SPA revealed that only one sample was incorrectly diagnosed, apparently because of operator error, when compared with conventional restriction fragment length polymorphism assay results. Conclusions: The SPA assay has potential for medium-scale mutation detection, having the advantage of being manipulatively simple and immediately adaptable for use in clinical laboratories with existing ELISA instrumentation.

scholarly journals Point mutation bias in SARS-CoV-2 variants results in increased ability to stimulate inflammatory responses

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Masato Kosuge ◽  
Emi Furusawa-Nishii ◽  
Koyu Ito ◽  
Yoshiro Saito ◽  
Kouetsu Ogasawara
Keyword(s):  
Severe Acute Respiratory Syndrome ◽  
Rna Editing ◽  
Inflammatory Responses ◽  
Rna Viruses ◽  
Point Mutations ◽  
Gene Mutations ◽  
Severe Pneumonia ◽  
Mutation Bias ◽  
Enhanced Production ◽  
Tnf Α

Abstract Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection induces severe pneumonia and is the cause of a worldwide pandemic. Coronaviruses, including SARS-CoV-2, have RNA proofreading enzymes in their genomes, resulting in fewer gene mutations than other RNA viruses. Nevertheless, variants of SARS-CoV-2 exist and may induce different symptoms; however, the factors and the impacts of these mutations are not well understood. We found that there is a bias to the mutations occurring in SARS-CoV-2 variants, with disproportionate mutation to uracil (U). These point mutations to U are mainly derived from cytosine (C), which is consistent with the substrate specificity of host RNA editing enzymes, APOBECs. We also found the point mutations which are consistent with other RNA editing enzymes, ADARs. For the C-to-U mutations, the context of the upstream uracil and downstream guanine from mutated position was found to be most prevalent. Further, the degree of increase of U in SARS-CoV-2 variants correlates with enhanced production of cytokines, such as TNF-α and IL-6, in cell lines when compared with stimulation by the ssRNA sequence of the isolated virus in Wuhan. Therefore, RNA editing is a factor for mutation bias in SARS-CoV-2 variants, which affects host inflammatory cytokines production.

scholarly journals Cell Culture Adaptation of Hepatitis C Virus and In Vivo Viability of an Adapted Variant

2007 ◽  
Vol 81 (23) ◽  
pp. 13168-13179 ◽  
Author(s):  
Artur Kaul ◽  
Ilka Woerz ◽  
Philip Meuleman ◽  
Geert Leroux-Roels ◽  
Ralf Bartenschlager
Keyword(s):  
Cell Culture ◽  
Hepatitis C Virus ◽  
Hepatitis C ◽  
Cultured Cells ◽  
Infectious Hepatitis ◽  
Adaptive Mutation ◽  
Viral Genomes ◽  
Adaptive Mutations ◽  
Spread Of Infection

ABSTRACT Production of infectious hepatitis C virus in cell culture has become possible because of the unique properties of the JFH1 isolate. However, virus titers are rather low, limiting the utility of this system. Here we describe the generation of cell culture-adapted JFH1 variants yielding higher titers of infectious particles and enhanced spread of infection in cultured cells. Sequence analysis of adapted genomes revealed a complex pattern of mutations that differed in two independent experiments. Adaptive mutations were observed both in the structural and in the nonstructural regions, with the latter having the highest impact on enhancement of virus titers. The major adaptive mutation was identified in NS5A, and it enhanced titers of three intergenotypic chimeras consisting of the structural region of a genotype 1a, 1b, or 3a isolate and the remainder of the JFH1 isolate. The mutation resides at the P3 position of the NS5A-B cleavage site and slows down processing, implying that subtle differences in replication complex formation appear to determine the efficiency of virus formation. Highly adapted JFH1 viruses carrying six mutations established a robust infection in uPA-transgenic SCID mice xenografted with human hepatocytes. However, the mutation in NS5A which enhanced virus titers in cell culture the most had reverted to wild type in nearly half of the viral genomes isolated from these animals at 15 weeks postinoculation. These results argue for some level of impaired fitness of this mutant in vivo.

scholarly journals Induction of a DNA Nickase in the Presence of Its Target Site Stimulates Adaptive Mutation in Escherichia coli

2002 ◽  
Vol 184 (20) ◽  
pp. 5599-5608 ◽  
Author(s):  
Cesar Rodriguez ◽  
Joshua Tompkin ◽  
Jill Hazel ◽  
Patricia L. Foster
Keyword(s):  
Escherichia Coli ◽  
Single Strand ◽  
Target Site ◽  
Adaptive Mutation ◽  
Target Sequence ◽  
Induced Mutations ◽  
Single Base ◽  
Adaptive Mutations ◽  
E Coli ◽  
Nicking Enzyme

ABSTRACT Adaptive mutation to Lac+ in Escherichia coli strain FC40 depends on recombination functions and is enhanced by the expression of conjugal functions. To test the hypothesis that the conjugal function that is important for adaptive mutation is the production of a single-strand nick at the conjugal origin, we supplied an exogenous nicking enzyme, the gene II protein (gIIp) of bacteriophage f1, and placed its target sequence near the lac allele. When both gIIp and its target site were present, adaptive mutation was stimulated three- to fourfold. Like normal adaptive mutations, gIIp-induced mutations were recA+ and ruvC+ dependent and were mainly single-base deletions in runs of iterated bases. In addition, gIIp with its target site could substitute for conjugal functions in adaptive mutation. These results support the hypothesis that nicking at the conjugal origin initiates the recombination that produces adaptive mutations in this strain of E. coli, and they suggest that nicking may be the only conjugal function required for adaptive mutation.

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