Immunodeficiency Virus Type-1 Reverse Transcriptase Research Articles

Biophysical Characterization of Novel DNA Aptamers against K103N/Y181C Double Mutant HIV-1 Reverse Transcriptase.

The human immunodeficiency virus type-1 Reverse Transcriptase (HIV-1 RT) plays a pivotal role in essential viral replication and is the main target for antiviral therapy. The anti-HIV-1 RT drugs address resistance-associated mutations. This research focused on isolating the potential specific DNA aptamers against K103N/Y181C double mutant HIV-1 RT. Five DNA aptamers showed low IC50 values against both the KY-mutant HIV-1 RT and wildtype (WT) HIV-1 RT. The kinetic binding affinity forms surface plasmon resonance of both KY-mutant and WT HIV-1 RTs in the range of 0.06–2 μM and 0.15–2 μM, respectively. Among these aptamers, the KY44 aptamer was chosen to study the interaction of HIV-1 RTs-DNA aptamer complex by NMR experiments. The NMR results indicate that the aptamer could interact with both WT and KY-mutant HIV-1 RT at the NNRTI drug binding pocket by inducing a chemical shift at methionine residues. Furthermore, KY44 could inhibit pseudo-HIV particle infection in HEK293 cells with nearly 80% inhibition and showed low cytotoxicity on HEK293 cells. These together indicated that the KY44 aptamer could be a potential inhibitor of both WT and KY-mutant HIV-RT.

An in silico molecular modeling approach of halolactone derivatives as potential inhibitors for human immunodeficiency virus type-1 reverse transcriptase enzyme

Acquired Immune Deficiency Syndrome (AIDS) is an infectious disease caused by Human Immunodeficiency Virus (HIV) infection and its replication requires the Reverse Transcriptase (RT) enzyme. RT plays a key role in the HIV life cycle, making it one of the most important targets for designing new drugs. Thus, in order to increase therapeutic options against AIDS, halolactone derivatives (D-halolactone) that have been showed as potential non-nucleoside inhibitors of the RT enzyme were studied. In the present work, a series of D-halolactone were investigated by molecular modeling studies, combining Three-dimensional Quantitative Structure-Activity Relationship (3 D-QSAR), molecular docking and Molecular Dynamics (MD) techniques, to understand the molecular characteristics that promote biological activity. The internal and external validation parameters indicated that the 3 D-QSAR model has good predictive capacity and statistical significance. Contour maps provided useful information on the structural characteristics of compounds for anti-HIV-1 activity. The docking results showed that D-halolactone present good complementarity by the RT allosteric site. In MD simulations it was observed that the formation of enzyme-ligand complexes were favorable, and from the free energy decomposition it was found that Leu100, Val106, Tyr181, Try188, and Trp229 are key residues for stabilization in the enzymatic site. Thus, the results showed that the proposed models can be used to design promising HIV-1 RT inhibitors. Communicated by Ramaswamy H. Sarma

An Overview of the Cure of HIV/AIDS Harbal Therapy Containing Natural Antioxidant, Vitamins and Minerals

Purposes: The unprecedented and sequence through which an estimate of 25 million lives have gone to their early grave yard through Acquired Immune-deficiency Syndrome HIV/AIDS can never be quantified; since, when it was first describes in 1981. In 2017/2018 by (UNAIDS) it was estimated globally for about 36.9millions people were living with Human, Immunodeficiency Virus (HIV) so to say. Henceforth the progress made in the field of treatment in the form of Antiretroviral Therapy (ART) disease has not been fully ascertain for the cure of HIV/AIDS; except, perpetual clinical suppressions. Thus, the current challenges that man kinds faces with the used of perpetual intake of antiretroviral therapy (clinical suppression)/artificial vaccine is un-justifiable. However, search for HIV therapy have open a new chapter in the search for novel drugs from Kaduna Polytechnic procedure. This review focuses on vitamins, antioxidant, mineral and supplement as sources of in-hibitors or eradications for human immunodeficiency virus type-1 (HIV) reverse transcriptase. Objective: To assess whether vitamins, antioxidant, minerals supplement are effective and safe in eradicating mortality and morbidity among populace with HIV infection. Selection criteria: Randomized control trials were selected that compared the effect of vitamins (A, C, D, E, K,), antioxidant, minerals and supplement with regard to treatment measures in HIV infected persons. Methods: To prevent authors bias, based on a systematic search of literature; anti-HIV reverse transcriptase activity of some plant’s species like those of Eucalyptus leaves, Garlic fresh fruits, Baobab leaves, aloe vera, neem leaves, moringa leaves, bitter leaves etc. respectively. Thus, these medicinal plants contain an appreciable or above values antioxidant compound or photochemical like those of Phenolic, anthraquinone, tannin, falconoid, terpenoid, lignin, coumarins etc. respectively. Contrarywise, these phytochemical compounds have been exploited traditionally for the cure of many diseases as well as inhibition of viral replication/transcription. Further investigations have shared more light through which phytochemicals compounds inhibit virus replication either during the viral entry inside the host cell or during their replication. Originality: in view of the current investigation or to accelerate drug discovery and innovation, this review recommends the urgent need to tap into the enrich locally available endogenous knowledge of putative anti- HIV/AIDS, photochemical and their derivatives, (reverse pharmacology, determine pan assay, interferences compounds, microbial enzyme metabolites relationship and their mechanisms to treat virial diseases.

DNA Tetrahedron Based Biosensor for Argonaute2 Assay in Single Cells and Human Immunodeficiency Virus Type-1 Related Ribonuclease H Detection in Vitro.

A well-designed DNA tetrahedron based biosensor (DTB) has been employed for imaging and detection of argonaute2 (Ago2), a key RNA interference (RNAi) protein. This DTB mainly contains two segments: DNA tetrahedron as a frame and a photoinduced electron-transfer (PET) pair as a fluorescence transducer. The DNA tetrahedral nanostructure is assembled with four nucleic acid strands. On one edge, one DNA strand forms a hairpin structure (RNA sequence) which is implanted in the two complementary double-strand DNAs, and the PET pairs, DNA/silver nanocluster (AgNC) and G-quadruplex/hemin complex, are labeled at the two termini of another DNA strand, respectively. The DNA tetrahedron structure forms a switchable scaffold that can present the functional DNA motifs in two different modes, according to the presence/absence of the target protein. The cleavage reaction by Ago2/miR-21 complex opens the hairpin structure, leading the PET pairs to be separated to each other in the spatial state. Thus, the DNA/AgNC fluorescence can be measured. By using this DTB, we obtained the 4.54 nM Ago2 detection limit and successful assay of Ago2/miR-21 complex in living cells. Also, the DTB was successfully employed for the further assay of RNase H, which plays an important role in the human immunodeficiency virus type-1 (HIV-1) reverse transcriptase pathway, with a limit of detection (LOD) of 3.41 U mL-1. Our DTB can be used as a device for the imaging protein concentration in single cells and has a potential value for disease diagnosis and treatment.

Challenges and approaches in the discovery of human immunodeficiency virus type-1 non-nucleoside reverse transcriptase inhibitors.

The type I human immunodeficiency virus (HIV-1) pandemic affecting over 37 million people worldwide continues, with 1.8 million people newly infected each year. Highly active antiretroviral therapy is efficient at reducing viral load and nearly one-half of the infected population is on treatment. One of the most successful approaches for the treatment of HIV infections is the use of inhibitors for human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT). At present, there are six nonnucleoside reverse transcriptase inhibitors (NNRTIs) approved for clinical use: nevirapine (NVP), delavirdine (DLV), efavirenz (EFV), etravirine (ETV), rilpivirine (RPV), and elsulfavirine. In this review, we will cover the development of different classes of NNRTIs over the last two decades. We will give an overview of traditional medicinal chemistry strategies for structural modification as bioisosterism principles, scaffold hopping, substitute decoration, and molecular hybridization. Furthermore, computer-aid design as virtual screening, de novo design and free-energy perturbation will be described in details.

Multiple-receptor conformation docking, dock pose clustering, and 3D QSAR-driven approaches exploring new HIV-1 RT inhibitors

Human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) plays a key in the life cycle of HIV-1. It is considered to be one of the promising targets for treating HIV/AIDS which contains two drug binding sites, a substrate binding site, and an allosteric site. Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are a class of RT inhibitors that bind to allosteric sites on HIV-1 RT in a non-competitive manner and thereby disrupting the conformation of RT. Hence, they can act as potent inhibitors against HIV-1 RT. In present study, the key structural requirements for enhancing HIV-1 RT inhibitory activity were explored from combined docking and three-dimensional quantitative structure activity relationship (3D QSAR) protocols. Initially, multiple-receptor conformation docking (MRCD) was performed using a series of diaryl pyridine and pyrimidine derivatives into the active site of ten X-ray crystal structures and one NMR-resolved conformation of HIV-1 RT. Later, the dock poses obtained from docking were clustered and 3D QSAR models were developed using comparative molecular field analysis (CoMFA) and comparative molecular similarity index analysis (CoMSIA) methods. Finally, a robust model was established using cross-validation techniques and the robustness of the model was confirmed through high accuracy of q2loo of 0.843 and 0.682, r2ncv of 0.977 and 0.949, and r2pred of 0.702 and 0.690, respectively, for CoMFA and CoMSIA. Based on the outcome of the results, new pyrimidine derivatives having potential inhibitory against HIV-1 RT were designed.

Inhibition of HIV-1 Reverse Transcriptase-Catalyzed Synthesis by Intercalated DNA Benzo[a]Pyrene 7,8-Dihydrodiol-9,10-Epoxide Adducts

To aid in the characterization of the relationship of structure and function for human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT), this investigation utilized DNAs containing benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE)-modified primers and templates as a probe of the architecture of this complex. BPDE lesions that differed in their stereochemistry around the C10 position were covalently linked to N 6-adenine and positioned in either the primer or template strand of a duplex template-primer. HIV-1 RT exhibited a stereoisomer-specific and strand-specific difference in replication when the BPDE-lesion was placed in the template versus the primer strand. When the C10 R-BPDE adduct was positioned in the primer strand in duplex DNA, 5 nucleotides from the 3΄ end of the primer terminus, HIV-1 RT could not fully replicate the template, producing truncated products; this block to further synthesis did not affect rates of dissociation or DNA binding affinity. Additionally, when the adducts were in the same relative position, but located in the template strand, similar truncated products were observed with both the C10 R and C10 S BPDE adducts. These data suggest that the presence of covalently-linked intercalative DNA adducts distant from the active site can lead to termination of DNA synthesis catalyzed by HIV-1 RT.

The impact of molecular manipulation in residue 114 of human immunodeficiency virus type-1 reverse transcriptase on dNTP substrate binding and viral replication

Human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) has a unique tight binding to dNTP substrates. Structural modeling of Ala-114 of HIV-1 RT suggests that longer side chains at this residue can reduce the space normally occupied by the sugar moiety of an incoming dNTP. Indeed, mutations at Ala-114 decrease the ability of RT to synthesize DNA at low dNTP concentrations and reduce the dNTP-binding affinity (Kd) of RT. However, the Kd values of WT and A114C RT remained equivalent with an acyclic dNTP substrate. Finally, mutant A114 RT HIV-1 vectors displayed a greatly reduced transduction in nondividing human lung fibroblasts (HLFs), while WT HIV-1 vector efficiently transduced both dividing and nondividing HLFs. Together these data support that the A114 residue of HIV-1 RT plays a key mechanistic role in the dNTP binding of HIV-1 RT and the unique viral infectivity of target cell types with low dNTP pools.

Lead optimization at C-2 and N-3 positions of thiazolidin-4-ones as HIV-1 non-nucleoside reverse transcriptase inhibitors

Based on rational drug design approach, a series of novel thiazolidin-4-ones bearing different aryl/heteroaryl moieties at position C-2 and N-3 are synthesized and evaluated as potent inhibitors for human immunodeficiency virus type-1 reverse transcriptase enzyme (HIV-1 RT). An in vitro HIV-1 RT assay showed that the compounds 4, 5, 6, 8, 12, 13, 14 and 17 have shown high inhibition of reverse transcriptase (75.41, 95.50, 98.07, 91.24, 85.27, 77.59, 84.11 & 76.49% inhibition) enzyme activity. Further, cell based assay showed that compounds 4, 5, 8 &12 are identified as the best compounds of the series (EC50 ranged from 0.09 to 0.8μg/ml and 0.12 to 1.06μg/ml) against HIV-1 IIIB and HIV-1 ADA5 strains, respectively. Moreover, the compounds which were active against HIV-1 IIIB and HIV-1 ADA5 were also found to be active against primary isolates (EC50 ranged from 0.10 to 1.55μg/ml against HIV-1 UG070 and 0.07 to 1.1μg/ml against HIV-1 VB59), respectively. Structure–activity relationship (SAR) studies demonstrated the importance of the lipophilic bulky substituent pattern on compact heteroaryl ring at N-3, replacement of C4′ at C-2 phenyl by trivalent bioisosteric nitrogen and dihalo groups at C-2 aryl/heteroaryl of thiazolidin-4-ones is crucial for anti-HIV-1 activity. Molecular modeling of compounds 4, 5, 8 and 12 in complex with HIV-1 RT demonstrate that there is good correlation of results obtained from SAR studies. Therefore the compounds 4, 5, 8 and 12 may be considered as good candidates for further optimization of anti-HIV-1 activity.

Compounds from rose (Rosa rugosa) flowers with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity

The aqueous extracts and ethanol precipitates of aqueous extracts of 18 medicinal herbs traditionally used in China were screened for their ability to inhibit human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) in-vitro. Among the samples screened at a concentration of 500 microg mL-1, dried rose (Rosa rugosa) flowers showed the strongest inhibition. The ethanol precipitate of the aqueous extract of R. rugosa was processed and two components (P1 and P2) were obtained after ion exchange chromatography on DEAE-cellulose. Then, P1-a (Mr 150 kDa) and P1-b (Mr 8 kDa) were isolated from P1 by gel filtration on Sephadex G-200. They inhibited the activity of HIV-1 RT with an IC50 of 158 nM and 148.16 microg mL-1 (18.5 microM), respectively. Further structural analyses revealed that P1-a was a polysaccharide-peptide complex, and P1-b was a polymer consisting of acteoside and acteoside derivatives identified by Fourier transform infrared spectroscopy, nuclear magnetic resonance, assays of carbohydrate and protein contents and high-performance liquid chromatography electrospray ionization mass spectrometry.

In Vitro HIV Type-1 Reverse Transcriptase Inhibitory Activity from Leaf Extracts of Scoparia dulcis L.

Aqueous and methanolic crude extracts of Scoparia dulcis L. leaves were screened for activity against human immunodeficiency virus (HIV) type-1 reverse transcriptase (RT) activity. The results were expressed as IC50. Zidovudine, which was used as a standard drug, showed an IC50 of 38.0 μg mL−1, whereas the aqueous and methanolic extracts from leaves of S. dulcis showed an IC50 of 60.0 and 47.0 μg mL−1, respectively. In this study, methanolic extract of S. dulcis leaves showed remarkable HIV type-1 reverse transcriptase inhibitory activity comparable to that of a standard such as zidovudine. Observed results using standardized parameters indicated that S. dulcis has promising HIV type-1 reverse transcriptase inhibitory activity.

3-O-Methylfunicone, a Selective Inhibitor of Mammalian Y-Family DNA Polymerases from an Australian Sea Salt Fungal Strain

We isolated a pol inhibitor from the cultured mycelia extract of a fungal strain isolated from natural salt from a sea salt pan in Australia, which was identified as 3-O-methylfunicone by spectroscopic analyses. This compound selectively inhibited the activities of mammalian Y-family DNA polymerases (pols) (i.e., pols η, ι and κ). Among these pols, human pol κ activity was most strongly inhibited, with an IC50 value of 12.5 μM. On the other hand, the compound barely influenced the activities of the other families of mammalian pols, such as A-family (i.e., pol γ), B-family (i.e., pols α, δ and ɛ) or X-family (i.e., pols β, λ and terminal deoxynucleotidyl transferase), and showed no effect on the activities of fish pol δ, plant pols, prokaryotic pols and other DNA metabolic enzymes, such as calf primase of pol α, human immunodeficiency virus type-1 (HIV-1) reverse transcriptase, human telomerase, T7 RNA polymerase, mouse IMP dehydrogenase (type II), human topoisomerases I and II, T4 polynucleotide kinase or bovine deoxyribonuclease I. This compound also suppressed the growth of two cultured human cancer cell lines, HCT116 (colon carcinoma cells) and HeLa (cervix carcinoma cells), and UV-treated HeLa cells exhibited lower clonogenic survival in the presence of inhibitor.

QSAR study of PETT derivatives as potent HIV-1 reverse transcriptase inhibitors

A series of phenylethylthiazolylthiourea (PETT) derivatives was subjected to quantitative structure–activity relationship (QSAR) analysis to find the structural requirements for ligand binding. The structural invariants used in this study were those obtained from whole molecular structures: chemical, quantum, topological, geometrical, constitutional and functional groups. Four chemometrics methods including multiple linear regressions (MLRs), factor analysis-MLR (FA-MLR), principal component regression analysis (PCRA) and partial least squares combined with genetic algorithm for variable selection (GA-PLS) were employed to make connections between structural parameters and enzyme inhibition. Using the pool of all types of calculated descriptors a QSAR model was derived for selected calibration set compounds indicating the importance of geometrical and chemical parameters on the Human Immunodeficiency Virus Type-1 (HIV-1) reverse transcriptase inhibitory activity. The results of FA-MLR analysis revealed the effects of geometrical and chemical indices on the inhibitory activity too. GA-PLS analysis showed the constitutional and geometrical indices to be the most significant parameters on inhibitory activity. A comparison between the different statistical methods employed indicated that PCRA represented superior results and it could explain and predict 74% and 79% of variances in the pIC 50 data, respectively.

Penicilliols A and B, novel inhibitors specific to mammalian Y-family DNA polymerases

Penicilliols A ( 1) and B ( 2) are novel 5-methoxy-3(2 H)-furanones isolated from cultures of a fungus ( Penicillium daleae K.M. Zalessky) derived from a sea moss, and their structures were determined by spectroscopic analyses. These compounds selectively inhibited activities of eukaryotic Y-family DNA polymerases (pols) (i.e., pols η, ι and κ), and compound 1 was a stronger inhibitor than compound 2. Among mammalian Y-family pols, mouse pol ι activity was most strongly inhibited by compounds 1 and 2, with IC 50 values of 19.8 and 32.5 μM, respectively. On the other hand, activities of many other pols, such as A-family (i.e., pol γ), B-family (i.e., pols α, δ and ε) or X-family (i.e., pols β, λ and terminal deoxynucleotidyl transferase), and some DNA metabolic enzymes, such as calf primase of pol α, human immunodeficiency virus type-1 (HIV-1) reverse transcriptase, human telomerase, T7 RNA polymerase, mouse IMP dehydrogenase (type II), human topoisomerases I and II, T4 polynucleotide kinase or bovine deoxyribonuclease I, are not influenced by these compounds. In conclusion, this is the first report on potent inhibitors of mammalian Y-family pols.

Human Immunodeficiency Virus type-1 reverse transcriptase exists as post-translationally modified forms in virions and cells

BackgroundHIV-1 reverse transcriptase (RT) is a heterodimer composed of p66 and p51 subunits and is responsible for reverse transcription of the viral RNA genome into DNA. RT can be post-translationally modified in vitro which may be an important mechanism for regulating RT activity. Here we report detection of different p66 and p51 RT isoforms by 2D gel electrophoresis in virions and infected cells.ResultsMajor isoforms of the p66 and p51 RT subunits were observed, with pI's of 8.44 and 8.31 respectively (p668.44 and p518.31). The same major isoforms were present in virions, virus-infected cell lysates and intracellular reverse transcription complexes (RTCs), and their presence in RTCs suggested that these are likely to be the forms that function in reverse transcription. Several minor RT isoforms were also observed. The observed pIs of the RT isoforms differed from the pI of theoretical unmodified RT (p668.53 and p518.60), suggesting that most of the RT protein in virions and cells is post-translationally modified. The modifications of p668.44 and p518.31 differed from each other indicating selective modification of the different RT subunits. The susceptibility of RT isoforms to phosphatase treatment suggested that some of these modifications were due to phosphorylation. Dephosphorylation, however, had no effect on in vitro RT activity associated with virions, infected cells or RTCs suggesting that the phospho-isoforms do not make a major contribution to RT activity in an in vitro assay.ConclusionThe same major isoform of p66 and p51 RT is found in virions, infected cells and RTC's and both of these subunits are post-translationally modified. This post-translational modification of RT may be important for the function of RT inside the cell.

2‐(2,6‐Dihalo‐phenyl)‐3‐heteroaryl‐2‐ylmethyl‐1, 3‐thiazolidin‐4‐ones: Anti‐HIV agents

A diversity of novel 2-aryl-3-heteroaryl-2-ylmethyl-1,3-thiazolidin-4-ones were designed and synthesized by reacting heteroaryl-2-ylmethyl amine with various 2,6-dihalosubstituted benzaldehydes and mercaptoacetic acid. The title compounds were evaluated for human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) inhibitory activity. The results of in vitro assays showed that some of the compounds were effective inhibitors of HIV-1 reverse transcriptase enzyme at micromolar concentrations with less cytotoxicity in both MT-4 cells as well as acutely infected human T-lymphoid CEM cells. Compounds 4h and 4k emerged as moderately more potent with EC(50) are at 0.20 and 0.21 microM as compared to reference parent compound thiazolobenzimidazoles EC(50) 0.35 microM in MT-4 cells.

Design and synthesis of 2-(2,6-dibromophenyl)-3-heteroaryl-1,3-thiazolidin-4-ones as anti-HIV agents

A series of 2-(2,6-dibromophenyl)-3-heteroaryl-1,3-thiazolidin-4-ones were designed, synthesized and evaluated as selective human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) enzyme inhibitors. The results of the HIV-1 RT kit and in vitro cell based assay showed that eight compounds effectively inhibited HIV-1 replication at 20–320 nM concentrations with minimal cytotoxicity in MT-4 as well as in CEM cells.

1-Deoxyrubralactone, a novel specific inhibitor of families X and Y of eukaryotic DNA polymerases from a fungal strain derived from sea algae

Talaroflavone ( 1) and 1-deoxyrubralactone ( 2) are natural compounds isolated from cultures of a fungal strain derived from sea algae, and their structures were determined by spectroscopic analyses. Compound 2 is a novel rubralactone derivative, 6-hydroxy-8-methoxy-1-methyl-1,2,3 a,9 b-tetrahydrocyclopenta[ c]isochromene-3,5-dione. These compounds selectively inhibited the activities of families X and Y of eukaryotic DNA polymerases (pols), and compound 2 was a stronger inhibitor than compound 1. The IC 50 values of compound 2 on rat pol β, which is a pol of family X, and human pol κ, which is a pol of family Y, were 11.9 and 59.8 μM, respectively. On the other hand, compounds 1 and 2 did not influence the activities of the other families of eukaryotic pols, such as family A (i.e., pol γ) and family B (i.e., pols α, δ, and ε), and showed no effect even on the activities of plant pols α and β, prokaryotic pols, and other DNA metabolic enzymes, such as calf primase of pol α, human immunodeficiency virus type-1 (HIV-1) reverse transcriptase, human telomerase, T7 RNA polymerase, mouse IMP dehydrogenase (type II), human topoisomerase I and II, T4 polynucleotide kinase, and bovine deoxyribonuclease I. This is the first report about the selective inhibitors of families X and Y of eukaryotic pols.

In vitro fidelity of the prototype primate foamy virus (PFV) RT compared to HIV-1 RT

We compared the in vitro fidelity of wild-type human immunodeficiency virus type-1 (HIV-1) reverse transcriptase (RT) and the prototype foamy virus (PFV) RT. Both enzymes had similar error rates for single nucleotide substitutions; however, PFV RT did not appear to make errors at specific hotspots, like HIV-1 RT. In addition, PFV RT made more deletions and insertions than HIV-1 RT. Although the majority of the missense errors made by HIV-1 RT and PFV RT are different, relatively few of the mutations caused by either enzyme can be explained by a misalignment/slippage mechanism. We suggest that the higher polymerase activity of PFV RT could contribute to the ability of the enzyme to jump to the same or a different template.

Nodulisporol and Nodulisporone, novel specific inhibitors of human DNA polymerase λ from a fungus, Nodulisporium sp.

Tetralols 1 and 2, dihydroisocoumarins 3– 6, and chromone 7 are natural compounds isolated from cultures of fungi, and their structures were determined by spectroscopic analyses. Compounds 1 and 2 from Nodulisporium sp. are novel tetralols, 1,2,3,4-tetrahydro-5-methoxynaphthalene-1,4-diol (nodulisporol) and 3,4-dihydro-4-hydroxy-8-methoxynaphthalen-1(2 H)-one (nodulisporone), respectively. All isolated compounds selectively inhibited the activity of human DNA polymerase λ (pol λ), and compound 5 (3,5-dimethyl-8-methoxy-3,4-dihydroisocoumarin) was the strongest inhibitor of pol λ in the tested compounds with an IC 50 value of 49 μM. New tetralols ( 1 and 2) are the third and second strongest inhibitors of pol λ, but did not influence the activities of mammalian pols α to κ, and showed no effect even on the activities of plant pols α and β, prokaryotic pols, and other DNA metabolic enzymes such as calf terminal deoxynucleotidyl transferase, human immunodeficiency virus type-1 (HIV-1) reverse transcriptase, human telomerase, T7 RNA polymerase, and bovine deoxyribonuclease I. The structure–activity relationships of isolated compounds such as novel tetralols, dihydroisocoumarins, and chromone are discussed.