scholarly journals Novel triterpenoids inhibit both DNA polymerase and DNA topoisomerase

2000 ◽  
Vol 350 (3) ◽  
pp. 757-763 ◽  
Author(s):  
Yoshiyuki MIZUSHINA ◽  
Akira IIDA ◽  
Keisuke OHTA ◽  
Fumio SUGAWARA ◽  
Kengo SAKAGUCHI
Keyword(s):  
Ursolic Acid ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Three Dimensional ◽  
Amino Acid Sequences ◽  
Dna Topoisomerases ◽  
Deoxyribonuclease I ◽  
Human Dna ◽  
Dna Binding Sites ◽  
Human Telomerase

As described previously, we found that new triterpenoid compounds, designated fomitellic acids A and B, which selectively inhibit the activities of mammalian DNA polymerases α and β [Mizushina, Tanaka, Kitamura, Tamai, Ikeda, Takemura, Sugawara, Arai, Matsukage, Yoshida and Sakaguchi (1998) Biochem. J. 330, 1325–1332; Tanaka, Kitamura, Mizushina, Sugawara and Sakaguchi (1998) J. Nat. Prod. 61, 193–197] and that a known triterpenoid, ursolic acid, is an inhibitor of human DNA topoisomerases I and II (A. Iida, Y. Mizushina and K. Sakaguchi, unpublished work). Here we report that all of these triterpenoids are potent inhibitors of calf DNA polymerase α, rat DNA polymerase β and human DNA topoisomerases I and II, and show moderate inhibitory effects on plant DNA polymerase II and human immunodeficiency virus reverse transcriptase. However, these compounds did not influence the activities of prokaryotic DNA polymerases such as Escherichia coli DNA polymerase I or other DNA metabolic enzymes such as human telomerase, T7 RNA polymerase and bovine deoxyribonuclease I. These triterpenoids were not only mammalian DNA polymerase inhibitors but also inhibitors of DNA topoisomerases I and II even though the enzymic characteristics of DNA polymerases and DNA topoisomerases, including their modes of action, amino acid sequences and three-dimensional structures, differed markedly. These triterpenoids did not bind to DNA, suggesting that they act directly on these enzymes. Because the three-dimensional structures of fomitellic acids were shown by computer simulation to be very similar to that of ursolic acid, the DNA-binding sites of both enzymes, which compete for the inhibitors, might be very similar. Fomitellic acid A and ursolic acid prevented the growth of NUGC cancer cells, with LD50 values of 38 and 30µM respectively.

Detection and characterization of DNA polymerase activity in Toxoplasma gondii

Parasitology ◽  
1993 ◽  
Vol 107 (2) ◽  
pp. 135-139 ◽  
Author(s):  
A. Makioka ◽  
B. Stavros ◽  
J. T. Ellis ◽  
A. M. Johnson
Keyword(s):  
Toxoplasma Gondii ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Sedimentation Coefficient ◽  
Polymerase Activity ◽  
Magnesium Ions ◽  
Dna Polymerase Β ◽  
Human Dna ◽  
Approximate Molecular Weight

SUMMARYA DNA polymerase activity has been detected and characterized in crude extracts from tachzoites of Toxoplasma gondii. The enzyme has a sedimentation coefficient of 6·4 S, corresponding to an approximate molecular weight of 150000 assuming a globular shape. Like mammalian DNA polymerase α, the DNA polymerase of T. gondii was sensitive to N-ethylmaleimide and inhibited by high ionic strength. However, the enzyme activity was not inhibited by aphidicolin which is an inhibitor of mammalian DNA polymerases α, δ and ε and also cytosine-β-D-arabinofuranoside-5′-triphosphate which is an inhibitor of α polymerase. The activity was inhibited by 2′,3′-dideoxythymidine-5′-triphosphate which is an inhibitor of mammalian DNA polymerase β and γ. Magnesium ions (Mg2+) were absolutely required for activity and its optimal concentration was 6 mM. The optimum potassium (K+) concentration was 50 mM and a higher concentration of K+ markedly inhibited the activity. Activity was optimal at pH 8. Monoclonal antibodies against human DNA polymerase did not bind to DNA polymerase of T. gondii. Thus the T. gondii enzyme differs from the human enzymes and may be a useful target for the design of toxoplasmacidal drugs.

scholarly journals DNA Polymerase: Structural Homology, Conformational Dynamics, and the Effects of Carcinogenic DNA Adducts

2010 ◽  
Vol 2010 ◽  
pp. 1-15 ◽  
Author(s):  
Richard G. Federley ◽  
Louis J. Romano
Keyword(s):  
Dna Replication ◽  
Dna Polymerase ◽  
Dna Adducts ◽  
Structural Changes ◽  
Dna Polymerases ◽  
Conformational Dynamics ◽  
Three Dimensional ◽  
Structural Homology ◽  
Human Right ◽  
Selection Of

DNA replication is vital for an organism to proliferate and lying at the heart of this process is the enzyme DNA polymerase. Most DNA polymerases have a similar three dimensional fold, akin to a human right hand, despite differences in sequence homology. This structural homology would predict a relatively unvarying mechanism for DNA synthesis yet various polymerases exhibit markedly different properties on similar substrates, indicative of each type of polymerase being prescribed to a specific role in DNA replication. Several key conformational steps, discrete states, and structural moieties have been identified that contribute to the array of properties the polymerases exhibit. The ability of carcinogenic adducts to interfere with conformational processes by directly interacting with the protein explicates the mutagenic consequences these adducts impose. Recent studies have identified novel states that have been hypothesised to test the fit of the nascent base pair, and have also shown the enzyme to possess a lively quality by continually sampling various conformations. This review focuses on the homologous structural changes that take place in various DNA polymerases, both replicative and those involved in adduct bypass, the role these changes play in selection of a correct substrate, and how the presence of bulky carcinogenic adducts affects these changes.

scholarly journals Human DNA Polymerase ι Promotes Replication through a Ring-Closed Minor-Groove Adduct That Adopts a syn Conformation in DNA

2005 ◽  
Vol 25 (19) ◽  
pp. 8748-8754 ◽  
Author(s):  
William T. Wolfle ◽  
Robert E. Johnson ◽  
Irina G. Minko ◽  
R. Stephen Lloyd ◽  
Satya Prakash ◽  
...  
Keyword(s):  
Dna Polymerase ◽  
Dna Polymerases ◽  
Minor Groove ◽  
Dna Lesions ◽  
Unsaturated Aldehyde ◽  
Cyclic Form ◽  
Human Dna ◽  
A Minor ◽  
Dna Polymerase Ι

ABSTRACT Acrolein, an α,β-unsaturated aldehyde, is generated in vivo as the end product of lipid peroxidation and from oxidation of polyamines. The reaction of acrolein with the N 2 group of guanine in DNA leads to the formation of a cyclic adduct, γ-hydroxy-1,N 2-propano-2′-deoxyguanosine (γ-HOPdG). Previously, we have shown that proficient replication through the γ-HOPdG adduct can be mediated by the sequential action of human DNA polymerases (Pols) ι and κ, in which Polι incorporates either pyrimidine opposite γ-HOPdG, but Polκ extends only from the cytosine. Since γ-HOPdG can adopt either a ring-closed cyclic form or a ring-opened form in DNA, to better understand the mechanisms that Pols ι and κ employ to promote replication through this lesion, we have examined the ability of these polymerases to replicate through the structural analogs of γ-HOPdG that are permanently either ring closed or ring opened. Our studies with these model adducts show that whereas the ring-opened form of γ-HOPdG is not inhibitory to synthesis by human Pols η, ι, or κ, only Polι is able to incorporate nucleotides opposite the ring-closed form, which is known to adopt a syn conformation in DNA. From these studies, we infer that (i) Pols η, ι, and κ have the ability to proficiently replicate through minor-groove DNA lesions that do not perturb the Watson-Crick hydrogen bonding of the template base with the incoming nucleotide, and (ii) Polι can accommodate a minor-groove-adducted template purine which adopts a syn conformation in DNA and forms a Hoogsteen base pair with the incoming nucleotide.

Incorporation of Selected Nucleoside Phosphonates and Anti-Human Immunodeficiency Virus Nucleotide Analogues into DNA by Human DNA Polymerases α, β and γ

1997 ◽  
Vol 8 (3) ◽  
pp. 187-195 ◽  
Author(s):  
T Cihlar ◽  
MS Chen
Keyword(s):  
Human Immunodeficiency Virus ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Dna Polymerase Β ◽  
Human Dna ◽  
Immunodeficiency Virus ◽  
Deoxynucleoside Triphosphate ◽  
Template Dna ◽  
Dna Polymerase Γ ◽  
Incorporation Efficiency

Incorporation of selected diphosphates of nucleoside phosphonates and triphosphates of currently approved anti-human immunodeficiency virus nucleoside analogues into DNA by human DNA polymerases α, β and γ was studied. All three polymerases were able to incorporate diphosphates of 9-(2-phosphonomethoxyethyl)adenine (PMEApp), 9-(2-phosphonomethoxyethyl)guanine (PMEGpp), ( R)-9-(2-phosphonomethoxypropyl)adenine (PMPApp), ( R)-9-(2-phosphononomethoxypropyl)-2,6-diaminopurine (PMPDAPpp) and ( 2R,5R)-9-[2,5-dihydro-5-(phosphonomethoxy)-2-furanyl]adenine (D4APpp) into primer/template DNA of defined sequence. After incorporation, these nucleoside phosphonates acted as terminators of primer extension. Kinetic constants of their incorporation were determined and compared with those for incorporation of ddATP, ddCTP, (-)-2′-deoxy-3′-thiacytidine triphosphate (3TC-TP), 2′,3′-didehydro-3′-deoxythymidine triphosphate (d4T-TP) and 3′-azido-3′-deoxythymidine triphosphate (AZT-TP). Relative efficiencies of incorporation (percentage of the incorporation efficiency for the corresponding natural deoxynucleoside triphosphate) by DNA polymerase a ranged from 0.05% for 3TC-TP to 51% for PMEGpp. DNA polymerase β catalysed the incorporation with relative efficiencies ranging from 0.014% for AZT-TP to 125% for ddCTP, and efficiencies of incorporation by DNA polymerase γ varied between 0.13% for 3TC-TP and 25% for ddCTP. Generally, the lowest incorporation efficiencies with all three polymerases were found for PMPApp (0.06–1.4%) and PMPDAPpp (0.075–2.2%).

scholarly journals Two Family B DNA Polymerases from Aeropyrum pernix, an Aerobic Hyperthermophilic Crenarchaeote

1999 ◽  
Vol 181 (19) ◽  
pp. 5984-5992 ◽  
Author(s):  
Isaac K. O. Cann ◽  
Sonoko Ishino ◽  
Norimichi Nomura ◽  
Yoshihiko Sako ◽  
Yoshizumi Ishino
Keyword(s):  
Amino Acid ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Amino Acid Sequences ◽  
Pol Ii ◽  
Aeropyrum Pernix ◽  
Heat Stable ◽  
Pol I ◽  
Group I ◽  
Fraction I

ABSTRACT DNA polymerase activities in fractionated cell extract ofAeropyrum pernix, a hyperthermophilic crenarchaeote, were investigated. Aphidicolin-sensitive (fraction I) and aphidicolin-resistant (fraction II) activities were detected. The activity in fraction I was more heat stable than that in fraction II. Two different genes (polA and polB) encoding family B DNA polymerases were cloned from the organism by PCR using degenerated primers based on the two conserved motifs (motif A and B). The deduced amino acid sequences from their entire coding regions contained all of the motifs identified in family B DNA polymerases for 3′→5′ exonuclease and polymerase activities. The product ofpolA gene (Pol I) was aphidicolin resistant and heat stable up to 80°C. In contrast, the product of polB gene (Pol II) was aphidicolin sensitive and stable at 95°C. These properties of Pol I and Pol II are similar to those of fractions II and I, respectively, and moreover, those of Pol I and Pol II ofPyrodictium occultum. The deduced amino acid sequence ofA. pernix Pol I exhibited the highest identities to archaeal family B DNA polymerase homologs found only in the crenarchaeotes (group I), while Pol II exhibited identities to homologs found in both euryarchaeotes and crenarchaeotes (group II). These results provide further evidence that the subdomainCrenarchaeota has two family B DNA polymerases. Furthermore, at least two DNA polymerases work in the crenarchaeal cells, as found in euryarchaeotes, which contain one family B DNA polymerase and one heterodimeric DNA polymerase of a novel family.

scholarly journals Kinetic Interaction of the Diphosphates of 9-(2-phosphonylmethoxyethyl)adenine and Other anti-HIV Active Purine Congeners with HIV Reverse Transcriptase and Human DNA Polymerases α, β and γ

1995 ◽  
Vol 6 (4) ◽  
pp. 217-221 ◽  
Author(s):  
J. M. Cherrington ◽  
S. J. W. Allen ◽  
N. Bischofberger ◽  
M. S. Chen
Keyword(s):  
Reverse Transcriptase ◽  
Dna Polymerase ◽  
Dna Polymerases ◽  
Inhibitory Effects ◽  
Hiv Reverse Transcriptase ◽  
Dna Polymerase Β ◽  
Human Dna ◽  
Dna Template ◽  
Anti Hiv ◽  
Micromolar Range

The inhibitory effects of the diphosphates of 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and its analogues on HIV reverse transcriptase and human DNA polymerases α, β, and γ have been studied. The analogues investigated are the diphosphates of 9-(2-phosphonylmethoxypropyl)adenine (PMPApp), 9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine (PMPDAPpp), and (2R,5R)-9-[2,5-dihydro-5-(phosphonyl methoxy)-2-furanyl]adenine (D4APpp). These four compounds are much more inhibitory to HIV reverse transcriptase when an RNA template rather than a DNA template is used. The Ki, values for the four compounds range from 11 to 22 nM with an RNA template. The Ki, values for ddCTP and AZTTP are 54 nM and 8 nM, respectively. PMEApp and its analogues show varying degrees of inhibition of the human DNA polymerases. The Ki, values for PMEApp, PMPApp and PMPDAPpp against DNA polymerase α are in the micromolar range, while D4APpp is a poor inhibitor of this enzyme with a Ki, value of 65.9 μM. The inhibition of DNA polymerase β by PMEApp, PMPApp and D4APpp is minimal, while PMPDAPpp shows higher inhibition of DNA polymerase β with a Ki, value of 9.71 μM. The Ki, values for PMEApp and D4APpp against DNA polymerase γ are submicromolar, while PMPApp and PMPDAPpp are much less inhibitory to this enzyme. For comparison, ddCTP was found to be a more potent inhibitor of DNA polymerases β and γ than the diphosphates of PMEA and its analogues.

scholarly journals Replication pastO6-Methylguanine by Yeast and Human DNA Polymerase η

2000 ◽  
Vol 20 (21) ◽  
pp. 8001-8007 ◽  
Author(s):  
Lajos Haracska ◽  
Satya Prakash ◽  
Louise Prakash
Keyword(s):  
Brain Tumors ◽  
Dna Polymerase ◽  
Double Mutant ◽  
Malignant Tumors ◽  
Alkylating Agents ◽  
Dna Polymerases ◽  
Clinical Effectiveness ◽  
Induced Mutations ◽  
Human Dna ◽  
Biochemical Studies

ABSTRACT O 6-Methylguanine (m6G) is formed by the action of alkylating agents such asN-methyl-N′-nitro-N-nitrosoguanidine (MNNG) on DNA. m6G is a highly mutagenic and carcinogenic lesion, and it presents a block to synthesis by DNA polymerases. Here, we provide genetic and biochemical evidence for the involvement of yeast and human DNA polymerase η (Polη) in the replicative bypass of m6G lesions in DNA. The formation of MNNG-induced mutations is almost abolished in therad30Δ pol32Δ double mutant of yeast, which lacks theRAD30 gene that encodes Polη and the Pol32 subunit of DNA polymerase δ (Polδ). Although Polδ can function in the mutagenic bypass of m6G lesions, our biochemical studies indicate that Polη is much more efficient in replicating through m6G than Polδ. Both Polη and Polδ insert a C or a T residue opposite from m6G; Polη, however, is more accurate, as it inserts a C about twice as frequently as Polδ. Alkylating agents are used in the treatment of malignant tumors, including lymphomas, brain tumors, melanomas, and gastrointestinal carcinomas, and the clinical effectiveness of these agents derives at least in part from their ability to form m6G in DNA. Inactivation of Polη could afford a useful strategy for enhancing the effectiveness of these agents in cancer chemotherapy.

Sign in / Sign up

Export Citation Format

Share Document