scholarly journals A rapidly reversible mutation generates subclonal genetic diversity and unstable drug resistance

2021 ◽  
Vol 118 (43) ◽  
pp. e2019060118
Author(s):  
Lufeng Dan ◽  
Yuze Li ◽  
Shuhua Chen ◽  
Jingbo Liu ◽  
Yu Wang ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Environmental Changes ◽  
Growth Defect ◽  
Common Mechanism ◽  
Evolutionary Divergence ◽  
Resistance Mutations ◽  
Genetic Changes ◽  
Clonal Population ◽  
Reading Frame ◽  
Correct Reading

Most genetic changes have negligible reversion rates. As most mutations that confer resistance to an adverse condition (e.g., drug treatment) also confer a growth defect in its absence, it is challenging for cells to genetically adapt to transient environmental changes. Here, we identify a set of rapidly reversible drug-resistance mutations in Schizosaccharomyces pombe that are caused by microhomology-mediated tandem duplication (MTD) and reversion back to the wild-type sequence. Using 10,000× coverage whole-genome sequencing, we identify nearly 6,000 subclonal MTDs in a single clonal population and determine, using machine learning, how MTD frequency is encoded in the genome. We find that sequences with the highest-predicted MTD rates tend to generate insertions that maintain the correct reading frame, suggesting that MTD formation has shaped the evolution of coding sequences. Our study reveals a common mechanism of reversible genetic variation that is beneficial for adaptation to environmental fluctuations and facilitates evolutionary divergence.

scholarly journals Rapidly reversible mutations generate subclonal genetic diversity and reversible drug resistance

2020 ◽  
Author(s):  
Lufeng Dan ◽  
Yuze Li ◽  
Shuhua Chen ◽  
Jingbo Liu ◽  
Fangting Li ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Environmental Changes ◽  
Growth Defect ◽  
Evolutionary Divergence ◽  
Resistance Mutations ◽  
Genetic Changes ◽  
Clonal Population ◽  
Reading Frame ◽  
Correct Reading ◽  
Type Sequence

AbstractMost genetic changes have negligible reversion rates. As most mutations that confer resistance to an adversary condition (e.g., drug treatment) also confer a growth defect in its absence, it is challenging for cells to genetically adapt to transient environmental changes. Here we identify a set of rapidly reversible drug resistance mutations in S. pombe that are caused by Microhomology mediated Tandem Duplication (MTD), and reversion back to the wild-type sequence. Using 10,000x coverage whole-genome sequencing we identify over 6000 subclonal MTDs in a single clonal population, and determine using machine learning how MTD frequency is encoded in DNA. We find that sequences with the highest predicted MTDs rates tend to generate insertions that maintain the correct reading frame; MTD formation has shaped the evolution of coding sequences. Our study reveals a mechanism of reversible genetic variation that is beneficial for adaptation to environmental fluctuations and facilitates evolutionary divergence.

scholarly journals 3′-Azido-3′-deoxythymidine drug resistance mutations in HIV-1 reverse transcriptase can induce long range conformational changes

1998 ◽  
Vol 95 (16) ◽  
pp. 9518-9523 ◽  
Author(s):  
Jingshan Ren ◽  
Robert M. Esnouf ◽  
Andrew L. Hopkins ◽  
E. Yvonne Jones ◽  
Ian Kirby ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Reverse Transcriptase ◽  
Long Range ◽  
Conformational Changes ◽  
Active Site ◽  
Common Mechanism ◽  
Resistance Mutations ◽  
Hiv Reverse Transcriptase ◽  
Drug Resistance Mutations ◽  
Hiv Rt

HIV reverse transcriptase (RT) is one of the main targets for the action of anti-AIDS drugs. Many of these drugs [e.g., 3′-azido-3′-deoxythymidine (AZT) and 2′,3′-dideoxyinosine (ddI)] are analogues of the nucleoside substrates used by the HIV RT. One of the main problems in anti-HIV therapy is the selection of a mutant virus with reduced drug sensitivity. Drug resistance in HIV is generated for nucleoside analogue inhibitors by mutations in HIV RT. However, most of these mutations are situated some distance from the polymerase active site, giving rise to questions concerning the mechanism of resistance. To understand the possible structural bases for this, the crystal structures of AZT- and ddI-resistant RTs have been determined. For the ddI-resistant RT with a mutation at residue 74, no significant conformational changes were observed for the p66 subunit. In contrast, for the AZT-resistant RT (RTMC) bearing four mutations, two of these (at 215 and 219) give rise to a conformational change that propagates to the active site aspartate residues. Thus, these drug resistance mutations produce an effect at the RT polymerase site mediated simply by the protein. It is likely that such long-range effects could represent a common mechanism for generating drug resistance in other systems.

Translation initiation in Archaea: conserved and domain-specific features

2011 ◽  
Vol 39 (1) ◽  
pp. 89-93 ◽  
Author(s):  
Dario Benelli ◽  
Paola Londei
Keyword(s):  
Start Codon ◽  
Translation Regulation ◽  
Evolutionary Divergence ◽  
Large Set ◽  
Initiation Mechanism ◽  
Reading Frame ◽  
Initiation Factors ◽  
Domain Specific ◽  
Correct Reading ◽  
Regulation Mechanisms

Initiation is a critical step in translation, during which the ribosome lands on the start codon and sets the correct reading frame for mRNA decoding. The rate and efficiency of translation are largely determined by initiation, which is therefore the preferred target of translation regulation mechanisms. Initiation has incurred an extensive evolutionary divergence among the primary domains of cell descent. The Archaea, albeit prokaryotes, have an initiation mechanism and apparatus more complex than those of the Bacteria; the molecular details of archaeal initiation are just beginning to be unravelled. The most notable aspects of archaeal initiation are the presence of two, perhaps three, distinct mechanisms for mRNA–ribosome interaction and the presence of a relatively large set of IFs (initiation factors), several of which are shared exclusively with the Eukarya. Among these, the protein termed a/eIF2 (archaeal/eukaryotic IF2) and aIF6 (archaeal IF6) are of special interest, since they appear to play key regulatory roles in the Eukarya. Studies of the function of these factors in Archaea have uncovered new features that will help to elucidate their conserved and domain-specific functions.

Genetic Diversity and Drug Resistance of HIV-1 CRF55_01B in Guangdong, China

2020 ◽  
Vol 18 (3) ◽  
pp. 210-218
Author(s):  
Guolong Yu ◽  
Yan Li ◽  
Xuhe Huang ◽  
Pingping Zhou ◽  
Jin Yan ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Drug Resistance ◽  
Reverse Transcriptase ◽  
Phylogenetic Analyses ◽  
Resistance Mutations ◽  
Protease Inhibition ◽  
Subtype B ◽  
Primary Drug Resistance ◽  
Hiv 1 ◽  
Primary Drug

Background: HIV-1 CRF55_01B was first reported in 2013. At present, no report is available regarding this new clade’s polymorphisms in its functionally critical regions protease and reverse transcriptase. Objective: To identify the diversity difference in protease and reverse transcriptase between CRF55_01B and its parental clades CRF01_AE and subtype B; and to investigate CRF55_01B’s drug resistance mutations associated with the protease inhibition and reverse transcriptase inhibition. Methods: HIV-1 RNA was extracted from plasma derived from a MSM population. The reverse transcription and nested PCR amplification were performed following our in-house PCR procedure. Genotyping and drug resistant-associated mutations and polymorphisms were identified based on polygenetic analyses and the usage of the HIV Drug Resistance Database, respectively. Results: A total of 9.24 % of the identified CRF55_01B sequences bear the primary drug resistance. CRF55_01B contains polymorphisms I13I/V, G16E and E35D that differ from those in CRF01_AE. Among the 11 polymorphisms in the RT region, seven were statistically different from CRF01_AE’s. Another three polymorphisms, R211K (98.3%), F214L (98.3%), and V245A/E (98.3 %.), were identified in the RT region and they all were statistically different with that of the subtype B. The V179E/D mutation, responsible for 100% potential low-level drug resistance, was found in all CRF55_01B sequences. Lastly, the phylogenetic analyses demonstrated 18 distinct clusters that account for 35% of the samples. Conclusions: CRF55_01B’s pol has different genetic diversity comparing to its counterpart in CRF55_01B’s parental clades. CRF55_01B has a high primary drug resistance presence and the V179E/D mutation may confer more vulnerability to drug resistance.

scholarly journals HIV Drug Resistance Mutations Detection by Next-Generation Sequencing during Antiretroviral Therapy Interruption in China

Pathogens ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 264
Author(s):  
Miaomiao Li ◽  
Shujia Liang ◽  
Chao Zhou ◽  
Min Chen ◽  
Shu Liang ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Next Generation Sequencing ◽  
Antiretroviral Therapy ◽  
Detection Threshold ◽  
Next Generation ◽  
Resistance Mutations ◽  
Hiv Drug Resistance ◽  
Drug Resistance Mutations ◽  
Therapy Interruption ◽  
Generation Sequencing

Patients with antiretroviral therapy interruption have a high risk of virological failure when re-initiating antiretroviral therapy (ART), especially those with HIV drug resistance. Next-generation sequencing may provide close scrutiny on their minority drug resistance variant. A cross-sectional study was conducted in patients with ART interruption in five regions in China in 2016. Through Sanger and next-generation sequencing in parallel, HIV drug resistance was genotyped on their plasma samples. Rates of HIV drug resistance were compared by the McNemar tests. In total, 174 patients were included in this study, with a median 12 (interquartile range (IQR), 6–24) months of ART interruption. Most (86.2%) of them had received efavirenz (EFV)/nevirapine (NVP)-based first-line therapy for a median 16 (IQR, 7–26) months before ART interruption. Sixty-one (35.1%) patients had CRF07_BC HIV-1 strains, 58 (33.3%) CRF08_BC and 35 (20.1%) CRF01_AE. Thirty-four (19.5%) of the 174 patients were detected to harbor HIV drug-resistant variants on Sanger sequencing. Thirty-six (20.7%), 37 (21.3%), 42 (24.1%), 79 (45.4%) and 139 (79.9) patients were identified to have HIV drug resistance by next-generation sequencing at 20% (v.s. Sanger, p = 0.317), 10% (v.s. Sanger, p = 0.180), 5% (v.s. Sanger, p = 0.011), 2% (v.s. Sanger, p < 0.001) and 1% (v.s. Sanger, p < 0.001) of detection thresholds, respectively. K65R was the most common minority mutation, of 95.1% (58/61) and 93.1% (54/58) in CRF07_BC and CRF08_BC, respectively, when compared with 5.7% (2/35) in CRF01_AE (p < 0.001). In 49 patients that followed-up a median 10 months later, HIV drug resistance mutations at >20% frequency such as K103N, M184VI and P225H still existed, but with decreased frequencies. The prevalence of HIV drug resistance in ART interruption was higher than 15% in the survey. Next-generation sequencing was able to detect more minority drug resistance variants than Sanger. There was a sharp increase in minority drug resistance variants when the detection threshold was below 5%.

scholarly journals Analysis of Low-Frequency Mutations Associated with Drug Resistance to Raltegravir before Antiretroviral Treatment

2010 ◽  
Vol 55 (3) ◽  
pp. 1114-1119 ◽  
Author(s):  
Jia Liu ◽  
Michael D. Miller ◽  
Robert M. Danovich ◽  
Nathan Vandergrift ◽  
Fangping Cai ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Treatment Failure ◽  
Low Frequency ◽  
Hiv Treatment ◽  
Viral Population ◽  
Virologic Suppression ◽  
Resistance Mutations ◽  
The Difference ◽  
Allele Specific Sequencing ◽  
Hiv 1

ABSTRACTRaltegravir is highly efficacious in the treatment of HIV-1 infection. The prevalence and impact on virologic outcome of low-frequency resistant mutations among HIV-1-infected patients not previously treated with raltegravir have not been fully established. Samples from HIV treatment-experienced patients entering a clinical trial of raltegravir treatment were analyzed using a parallel allele-specific sequencing (PASS) assay that assessed six primary and six secondary integrase mutations. Patients who achieved and sustained virologic suppression (success patients,n= 36) and those who experienced virologic rebound (failure patients,n= 35) were compared. Patients who experienced treatment failure had twice as many raltegravir-associated resistance mutations prior to initiating treatment as those who achieved sustained virologic success, but the difference was not statistically significant. The frequency of nearly all detected resistance mutations was less than 1% of viral population, and the frequencies of mutations between the success and failure groups were similar. Expansion of pre-existing mutations (one primary and five secondary) was observed in 16 treatment failure patients in whom minority resistant mutations were detected at baseline, suggesting that they might play a role in the development of drug resistance. Two or more mutations were found in 13 patients (18.3%), but multiple mutations were not present in any single viral genome by linkage analysis. Our study demonstrates that low-frequency primary RAL-resistant mutations were uncommon, while minority secondary RAL-resistant mutations were more frequently detected in patients naïve to raltegravir. Additional studies in larger populations are warranted to fully understand the clinical implications of these mutations.

scholarly journals Amelioration of the Cost of Conjugative Plasmid Carriage in Eschericha coli K12

Genetics ◽  
2003 ◽  
Vol 165 (4) ◽  
pp. 1641-1649
Author(s):  
Cecilia Dahlberg ◽  
Lin Chao
Keyword(s):  
Drug Resistance ◽  
Multiple Drug Resistance ◽  
Conjugative Plasmid ◽  
Energetic Cost ◽  
Multiple Drug ◽  
Genetic Changes ◽  
Batch Cultures ◽  
Transfer Rates ◽  
Bacterial Plasmid ◽  
The Cost

Abstract Although plasmids can provide beneficial functions to their host bacteria, they might confer a physiological or energetic cost. This study examines how natural selection may reduce the cost of carrying conjugative plasmids with drug-resistance markers in the absence of antibiotic selection. We studied two plasmids, R1 and RP4, both of which carry multiple drug resistance genes and were shown to impose an initial fitness cost on Escherichia coli. To determine if and how the cost could be reduced, we subjected plasmid-containing bacteria to 1100 generations of evolution in batch cultures. Analysis of the evolved populations revealed that plasmid loss never occurred, but that the cost was reduced through genetic changes in both the plasmids and the bacteria. Changes in the plasmids were inferred by the demonstration that evolved plasmids no longer imposed a cost on their hosts when transferred to a plasmid-free clone of the ancestral E. coli. Changes in the bacteria were shown by the lowered cost when the ancestral plasmids were introduced into evolved bacteria that had been cured of their (evolved) plasmids. Additionally, changes in the bacteria were inferred because conjugative transfer rates of evolved R1 plasmids were lower in the evolved host than in the ancestral host. Our results suggest that once a conjugative bacterial plasmid has invaded a bacterial population it will remain even if the original selection is discontinued.

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