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Mitochondrion Nov 2015Mitochondrial bioenergetics, mitochondrial reactive oxygen species (ROS) and cellular levels of nucleotides have been hypothesized as early indicators of Alzheimer's...
Mitochondrial bioenergetics, mitochondrial reactive oxygen species (ROS) and cellular levels of nucleotides have been hypothesized as early indicators of Alzheimer's disease (AD). Utilizing relative decline of cognitive ability as a predictor of AD risk, we evaluated the correlation between change of cognitive ability and mitochondrial bioenergetics, ROS and cellular levels of deoxyribonucleotides. Change of cognitive abilities, scored at ages of approximately 20 and 57 was determined for a cohort of 1985 male participants. Mitochondrial bioenergetics, mitochondrial ROS and whole-cell levels of deoxyribonucleotide triphosphates were measured in peripheral blood mononuclear cells (PBMCs) from a total of 103 selected participants displaying the most pronounced relative cognitive decline and relative cognitive improvement. We show that relative cognitive decline is associated with higher PBMC content of deoxythymidine-triphosphate (dTTP) (20%), but not mitochondrial bioenergetics parameters measured in this study or mitochondrial ROS. Levels of dTTP in PBMCs are indicators of relative cognitive change suggesting a role of deoxyribonucleotides in the etiology of AD.
Topics: Alzheimer Disease; Cohort Studies; Energy Metabolism; Humans; Leukocytes, Mononuclear; Male; Mitochondria; Reactive Oxygen Species; Thymine Nucleotides
PubMed: 26408413
DOI: 10.1016/j.mito.2015.09.002 -
Nucleic Acids Research Feb 2021Replication forks often stall at damaged DNA. To overcome these obstructions and complete the DNA duplication in a timely fashion, replication can be restarted...
Replication forks often stall at damaged DNA. To overcome these obstructions and complete the DNA duplication in a timely fashion, replication can be restarted downstream of the DNA lesion. In mammalian cells, this repriming of replication can be achieved through the activities of primase and polymerase PrimPol. PrimPol is stimulated in DNA synthesis through interaction with PolDIP2, however the exact mechanism of this PolDIP2-dependent stimulation is still unclear. Here, we show that PrimPol uses a flexible loop to interact with the C-terminal ApaG-like domain of PolDIP2, and that this contact is essential for PrimPol's enhanced processivity. PolDIP2 increases primer-template and dNTP binding affinities of PrimPol, which concomitantly enhances its nucleotide incorporation efficiency. This stimulation is dependent on a unique arginine cluster in PolDIP2. Since the polymerase activity of PrimPol alone is very limited, this mechanism, where the affinity for dNTPs gets increased by PolDIP2 binding, might be critical for the in vivo function of PrimPol in tolerating DNA lesions at physiological nucleotide concentrations.
Topics: Amino Acid Motifs; Arginine; DNA; DNA Primase; DNA-Directed DNA Polymerase; Deoxyribonucleotides; Models, Molecular; Multifunctional Enzymes; Nuclear Proteins; Protein Binding
PubMed: 33533925
DOI: 10.1093/nar/gkab049 -
Nucleic Acids Research Apr 2010Eukaryotic cells contain a delicate balance of minute amounts of the four deoxyribonucleoside triphosphates (dNTPs), sufficient only for a few minutes of DNA...
Eukaryotic cells contain a delicate balance of minute amounts of the four deoxyribonucleoside triphosphates (dNTPs), sufficient only for a few minutes of DNA replication. Both a deficiency and a surplus of a single dNTP may result in increased mutation rates, faulty DNA repair or mitochondrial DNA depletion. dNTPs are usually quantified by an enzymatic assay in which incorporation of radioactive dATP (or radioactive dTTP in the assay for dATP) into specific synthetic oligonucleotides by a DNA polymerase is proportional to the concentration of the unknown dNTP. We find that the commonly used Klenow DNA polymerase may substitute the corresponding ribonucleotide for the unknown dNTP leading in some instances to a large overestimation of dNTPs. We now describe assay conditions for each dNTP that avoid ribonucleotide incorporation. For the dTTP and dATP assays it suffices to minimize the concentrations of the Klenow enzyme and of labeled dATP (or dTTP); for dCTP and dGTP we had to replace the Klenow enzyme with either the Taq DNA polymerase or Thermo Sequenase. We suggest that in some earlier reports ribonucleotide incorporation may have caused too high values for dGTP and dCTP.
Topics: Cell Extracts; Cytidine Triphosphate; DNA Polymerase I; DNA-Directed DNA Polymerase; Deoxycytosine Nucleotides; Deoxyguanine Nucleotides; Deoxyribonucleotides; Humans; Ribonucleotides; Taq Polymerase
PubMed: 20008099
DOI: 10.1093/nar/gkp1141 -
Nucleic Acids Research Jun 2014The transmission of genetic information relies on Watson-Crick base pairing between nucleoside phosphates and template bases in template-primer complexes. Enzyme-free...
The transmission of genetic information relies on Watson-Crick base pairing between nucleoside phosphates and template bases in template-primer complexes. Enzyme-free primer extension is the purest form of the transmission process, without any chaperon-like effect of polymerases. This simple form of copying of sequences is intimately linked to the origin of life and provides new opportunities for reading genetic information. Here, we report the dissociation constants for complexes between (deoxy)nucleotides and template-primer complexes, as determined by nuclear magnetic resonance and the inhibitory effect of unactivated nucleotides on enzyme-free primer extension. Depending on the sequence context, Kd's range from 280 mM for thymidine monophosphate binding to a terminal adenine of a hairpin to 2 mM for a deoxyguanosine monophosphate binding in the interior of a sequence with a neighboring strand. Combined with rate constants for the chemical step of extension and hydrolytic inactivation, our quantitative theory explains why some enzyme-free copying reactions are incomplete while others are not. For example, for GMP binding to ribonucleic acid, inhibition is a significant factor in low-yielding reactions, whereas for amino-terminal DNA hydrolysis of monomers is critical. Our results thus provide a quantitative basis for enzyme-free copying.
Topics: DNA; DNA Primers; Deoxyribonucleotides; Templates, Genetic
PubMed: 24875480
DOI: 10.1093/nar/gku314 -
Journal of Molecular Biology Dec 2018Consistent with the fact that ribonucleotides (rNTPs) are in excess over deoxyribonucleotides (dNTPs) in vivo, recent findings indicate that replicative DNA polymerases...
Consistent with the fact that ribonucleotides (rNTPs) are in excess over deoxyribonucleotides (dNTPs) in vivo, recent findings indicate that replicative DNA polymerases (DNA Pols) are able to insert ribonucleotides (rNMPs) during DNA synthesis, raising crucial questions about the fidelity of DNA replication in both Bacteria and Eukarya. Here, we report that the level of rNTPs is 20-fold higher than that of dNTPs in Pyrococcus abyssi cells. Using dNTP and rNTP concentrations present in vivo, we recorded rNMP incorporation in a template-specific manner during in vitro synthesis, with the family-D DNA Pol (PolD) having the highest propensity compared with the family-B DNA Pol and the p41/p46 complex. We also showed that ribonucleotides accumulate at a relatively high frequency in the genome of wild-type Thermococcales cells, and this frequency significantly increases upon deletion of RNase HII, the major enzyme responsible for the removal of RNA from DNA. Because ribonucleotides remain in genomic DNA, we then analyzed the effects on polymerization activities by the three DNA Pols. Depending on the identity of the base and the sequence context, all three DNA Pols bypass rNMP-containing DNA templates with variable efficiency and nucleotide (mis)incorporation ability. Unexpectedly, we found that PolD correctly base-paired a single ribonucleotide opposite rNMP-containing DNA templates. An evolutionary scenario is discussed concerning rNMP incorporation into DNA and genome stability.
Topics: Archaeal Proteins; DNA Replication; DNA, Archaeal; DNA-Directed DNA Polymerase; Deoxyribonucleotides; Genomic Instability; Ribonucleotides; Thermococcales
PubMed: 30342933
DOI: 10.1016/j.jmb.2018.10.004 -
RNA (New York, N.Y.) Aug 1997The contribution of the ribose 2'-hydroxyls to RNA structure and function has been analyzed, but still remains controversial. In this work, we report the use of a mutant...
The contribution of the ribose 2'-hydroxyls to RNA structure and function has been analyzed, but still remains controversial. In this work, we report the use of a mutant T7 RNA polymerase as a tool in RNA studies, applied to the aspartate and methionine tRNA aminoacylation systems from yeast. Our approach consists of determining the effect of substituting natural ribonucleotides by deoxyribonucleotides in RNA and, thereby, defining the subset of important 2'-hydroxyl groups. We show that deoxyribose-containing RNA can be folded in a global conformation similar to that of natural RNA. Melting curves of tRNAs, obtained by temperature-gradient gel electrophoresis, indicate that in deoxyribo-containing molecules, the thermal stability of the tertiary network drops down, whereas the stability of the secondary structure remains unaltered. Nuclease footprinting reveals a significant increase in the accessibility of both single- and double-stranded regions. As to the functionality of the deoxyribose-containing tRNAs, their in vitro aminoacylation efficiency indicates striking differential effects depending upon the nature of the substituted ribonucleotides. Strongest decrease in charging occurs for yeast initiator tRNA(Met) transcripts containing dG or dC residues and for yeast tRNA(Asp) transcripts with dU or dG. In the aspartate system, the decreased aminoacylation capacities can be correlated with the substitution of the ribose moieties of U11 and G27, disrupting two hydrogen bond contacts with the synthetase. Altogether, this suggests that specific 2'-hydroxyl groups in tRNAs can act as determinants specifying aminoacylation identity.
Topics: Base Sequence; DNA-Directed RNA Polymerases; Deoxyribonucleotides; Models, Molecular; Molecular Sequence Data; Mutation; Nucleic Acid Conformation; RNA, Transfer; RNA, Transfer, Asp; RNA, Transfer, Met; Structure-Activity Relationship; Transcription, Genetic; Viral Proteins
PubMed: 9257648
DOI: No ID Found -
Journal of Bacteriology Oct 1993
Review
Topics: Bacteriophage T4; DNA, Viral; Deoxyribonucleotides; Enzymes; Kinetics; Macromolecular Substances
PubMed: 8407814
DOI: 10.1128/jb.175.20.6377-6381.1993 -
Applied and Environmental Microbiology May 2015Analysis of the genome of Bacillus halodurans strain C125 indicated that two pathways leading from a cytosine deoxyribonucleotide to dUMP, used for dTMP synthesis, were...
Analysis of the genome of Bacillus halodurans strain C125 indicated that two pathways leading from a cytosine deoxyribonucleotide to dUMP, used for dTMP synthesis, were encoded by the genome of the bacterium. The genes that were responsible, the comEB gene and the dcdB gene, encoding dCMP deaminase and the bifunctional dCTP deaminase:dUTPase (DCD:DUT), respectively, were both shown to be expressed in B. halodurans, and both genes were subject to repression by the nucleosides thymidine and deoxycytidine. The latter nucleoside presumably exerts its repression after deamination by cytidine deaminase. Both comEB and dcdB were cloned, overexpressed in Escherichia coli, and purified to homogeneity. Both enzymes were active and displayed the expected regulatory properties: activation by dCTP for dCMP deaminase and dTTP inhibition for both enzymes. Structurally, the B. halodurans enzyme resembled the Mycobacterium tuberculosis enzyme the most. An investigation of sequenced genomes from other species of the genus Bacillus revealed that not only the genome of B. halodurans but also the genomes of Bacillus pseudofirmus, Bacillus thuringiensis, Bacillus hemicellulosilyticus, Bacillus marmarensis, Bacillus cereus, and Bacillus megaterium encode both the dCMP deaminase and the DCD:DUT enzymes. In addition, eight dcdB homologs from Bacillus species within the genus for which the whole genome has not yet been sequenced were registered in the NCBI Entrez database.
Topics: Amino Acid Sequence; Bacillus; Bacterial Proteins; Biosynthetic Pathways; Crystallography, X-Ray; Cytosine; DCMP Deaminase; Deoxyribonucleotides; Deoxyuracil Nucleotides; Kinetics; Molecular Sequence Data; Nucleotide Deaminases; Substrate Specificity
PubMed: 25746996
DOI: 10.1128/AEM.00268-15 -
Postepy Biochemii Jun 2019High replication fidelity, understood as the DNA polymerases’ ability to select nucleotides with both correct base and sugar, is of critical importance for maintaining... (Review)
Review
High replication fidelity, understood as the DNA polymerases’ ability to select nucleotides with both correct base and sugar, is of critical importance for maintaining the genetic stability. Due to the fact that the cellular levels of ribonucleotides are much higher than the concentrations of deoxyribonucleotides, replicative polymerases are able to incorporate ribonucleotides with up to 1000-fold higher frequency than mismatched deoxyribonucleotides. The ability to discriminate against ribonucleotides by the DNA polymerases relies on the steric gate residue in the enzyme’s catalytic centre. Despite the fact that ribonucleotides are the most abundantly inserted incorrect nucleotides in DNA, they are not observed in properly functioning cells. The major pathway responsible for the recognition and removal of ribonucleotides from DNA is called Ribonucleotide Excision Repair. The impairment of ribonucleotide removal pathways can cause increased mutation rate, replication stress, DNA breakage, problems with transcription, chromatin structure maintenance, genetic disorders and cell death. In spite of that, ribonucleotide incorporation into DNA may have some positive biological impact, stimulating mismatch repair and non-homologous end joining.
Topics: DNA; DNA Repair; DNA Replication; DNA-Directed DNA Polymerase; Deoxyribonucleotides; Genomic Instability; Ribonucleotides
PubMed: 31642653
DOI: 10.18388/pb.2019_247 -
BMC Medical Research Methodology Nov 2019Antiretroviral therapy (ART) has significantly reduced HIV-related morbidity and mortality. However, therapeutic benefit of ART is often limited by delayed... (Comparative Study)
Comparative Study
A comparison of machine learning techniques for classification of HIV patients with antiretroviral therapy-induced mitochondrial toxicity from those without mitochondrial toxicity.
BACKGROUND
Antiretroviral therapy (ART) has significantly reduced HIV-related morbidity and mortality. However, therapeutic benefit of ART is often limited by delayed drug-associated toxicity. Nucleoside reverse transcriptase inhibitors (NRTIs) are the backbone of ART regimens. NRTIs compete with endogenous deoxyribonucleotide triphosphates (dNTPs) in incorporation into elongating DNA chain resulting in their cytotoxic or antiviral effect. Thus, the efficacy of NRTIs could be affected by direct competition with endogenous dNTPs and/or feedback inhibition of their metabolic enzymes. In this paper, we assessed whether the levels of ribonucleotides (RN) and dNTP pool sizes can be used as biomarkers in distinguishing between HIV-infected patients with ART-induced mitochondrial toxicity and HIV-infected patients without toxicity.
METHODS
We used data collected through a case-control study from 50 subjects. Cases were defined as HIV-infected individuals with clinical and/or laboratory evidence of mitochondrial toxicity. Each case was age, gender, and race matched with an HIV-positive without evidence of toxicity. We used a range of machine learning procedures to distinguish between patients with and without toxicity. Using resampling methods like Monte Carlo k-fold cross validation, we compared the accuracy of several machine learning algorithms applied to our data. We used the algorithm with highest classification accuracy rate in evaluating the diagnostic performance of 12 RN and 14 dNTP pool sizes as biomarkers of mitochondrial toxicity.
RESULTS
We used eight classification algorithms to assess the diagnostic performance of RN and dNTP pool sizes distinguishing HIV patients with and without NRTI-associated mitochondrial toxicity. The algorithms resulted in cross-validated classification rates of 0.65-0.76 for dNTP and 0.72-0.83 for RN, following reduction of the dimensionality of the input data. The reduction of input variables improved the classification performance of the algorithms, with the most pronounced improvement for RN. Complex tree-based methods worked the best for both the deoxyribose dataset (Random Forest) and the ribose dataset (Classification Tree and AdaBoost), but it is worth noting that simple methods such as Linear Discriminant Analysis and Logistic Regression were very competitive in terms of classification performance.
CONCLUSIONS
Our finding of changes in RN and dNTP pools in participants with mitochondrial toxicity validates the importance of dNTP pools in mitochondrial function. Hence, levels of RN and dNTP pools can be used as biomarkers of ART-induced mitochondrial toxicity.
Topics: Algorithms; Anti-Retroviral Agents; Biomarkers; Case-Control Studies; Deoxyribonucleotides; Dideoxynucleotides; HIV Infections; Humans; Machine Learning; Ribonucleotides
PubMed: 31775643
DOI: 10.1186/s12874-019-0848-z