Dipeptide alcohol-based inhibitors of eukaryotic DNA polymerase α

The effects of avermectin on amino acid neurotransmitters and their receptors in the pigeon brain

The objective of this study was to examine the effects of avermectin (AVM) on amino acid neurotransmitters and their receptors in the pigeon brain. Four groups two-month-old American king pigeons (n=20/group) were fed either a commercial diet or an AVM-supplemented diet (20mg/kg·diet, 40 mg/kg·diet, or 60 mg/kg·diet) for 30, 60, or 90 days. The contents of aspartic acid (ASP), glutamate (GLU), glycine (GLY), and γ-aminobutyric acid (GABA) in the brain tissues were determined using ultraviolet high-performance liquid chromatography (HPLC). The expression levels of the GLU and GABA receptor genes were analyzed using real-time quantitative polymerase chain reaction (qPCR). The results indicate that AVM exposure significantly enhances the contents of GABA, GLY, GLU, and ASP in the cerebrum, cerebellum, and optic lobe. In addition, AVM exposure increases the mRNA expression levels of γ-aminobutyric acid type A receptor (GABAAR), γ-aminobutyric acid type B receptor (GABABR), N-methyl-d-aspartate 1 receptor (NR1), N-methyl-d-aspartate 2A receptor (NR2A), and N-methyl-d-aspartate 2B receptor (NR2B) in a dose- and time-dependent manner. Moreover, we found that the most damaged organ was the cerebrum, followed by the cerebellum, and then the optic lobe. These results show that the AVM-induced neurotoxicity may be associated with its effects on amino acid neurotransmitters and their receptors. The information presented in this study will help supplement the available data for future AVM toxicity studies.

Alkyl sulfonyl derivatized PAMAM-G2 dendrimers as nonviral gene delivery vectors with improved transfection efficiencies

Amphiphilic dendrimer-based gene delivery vectors bearing peripheral alkyl sulfonyl hydrophobic tails were constructed using low-generation PAMAM-G2 as the core and functionalized by means of the aza-Michael type addition of its primary amino groups to vinylsulfone derivatives as an efficient tool for surface engineering. While the unmodified PAMAM-G2 was unable to efficiently transfect eukaryotic cells, functionalized PAMAM-G2 dendrimers were able to bind DNA at low N/P ratios, protect DNA from digestion with DNase I and showed high transfection efficiencies and low cytotoxicity. Dendrimers with a C18 alkyl chain produced transfection efficiencies up to 3.1 fold higher than LipofectAMINE™ 2000 in CHO-k1 cells. The dendriplexes based in functionalized PAMAM-G2 also showed the ability to retain their transfection properties in the presence of serum and the ability to transfect different eukaryotic cell lines such as Neuro-2A and RAW 264.7. Taking advantage of the vinylsulfone chemistry, fluorescent PAMAM-G2 derivatives of these vectors were prepared as molecular probes to determine cellular uptake and internalization through a clathrin-independent mechanism.

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 eta, iota and kappa). Among these pols, human pol kappa activity was most strongly inhibited, with an IC(50) value of 12.5 microM. On the other hand, the compound barely influenced the activities of the other families of mammalian pols, such as A-family (i.e., pol gamma), B-family (i.e., pols alpha, delta and epsilon) or X-family (i.e., pols beta, lambda and terminal deoxynucleotidyl transferase), and showed no effect on the activities of fish pol delta, plant pols, prokaryotic pols and other DNA metabolic enzymes, such as calf primase of pol alpha, 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.

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

Penicilliols A (1) and B (2) are novel 5-methoxy-3(2H)-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 eta, iota and kappa), and compound 1 was a stronger inhibitor than compound 2. Among mammalian Y-family pols, mouse pol iota activity was most strongly inhibited by compounds 1 and 2, with IC(50) values of 19.8 and 32.5 microM, respectively. On the other hand, activities of many other pols, such as A-family (i.e., pol gamma), B-family (i.e., pols alpha, delta and epsilon) or X-family (i.e., pols beta, lambda and terminal deoxynucleotidyl transferase), and some DNA metabolic enzymes, such as calf primase of pol alpha, 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.

Hymenoic acid, a novel specific inhibitor of human DNA polymerase lambda from a fungus of Hymenochaetaceae sp

Hymenoic acid (1) is a natural compound isolated from cultures of a fungus, Hymenochaetaceae sp., and this structure was determined by spectroscopic analyses. Compound 1 is a novel sesquiterpene, trans-4-[(1'E,5'S)-5'-carboxy-1'-methyl-1'-hexenyl]cyclohexanecarboxylic acid. This compound selectively inhibited the activity of human DNA polymerase lambda (pol lambda) in vitro, and 50% inhibition was observed at a concentration of 91.7microM. Compound 1 did not influence the activities of the other seven mammalian pols (i.e., pols alpha, gamma, delta, epsilon, eta, iota, and kappa), but also showed no effect even on the activity of pol beta, which is thought to have a very similar three-dimensional structure to the pol beta-like region of pol lambda. This compound also did not inhibit the activities of prokaryotic pols and other DNA metabolic enzymes tested. These results suggested that compound 1 could be a selective inhibitor of eukaryotic pol lambda. This compound had no inhibitory activities against two N-terminal truncated pol lambda, del-1 pol lambda (lacking nuclear localization signal (NLS), BRCA1 C-terminus (BRCT) domain [residues 133-575]), and del-2 pol lambda (lacking NLS, BRCT, domain and proline-rich region [residues 245-575]). The compound 1-induced inhibition of intact pol lambda activity was non-competitive with respect to both the DNA template-primer and the dNTP substrate. On the basis of these results, the pol lambda inhibitory mechanism of compound 1 is discussed.

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(2H)-one (nodulisporone), respectively. All isolated compounds selectively inhibited the activity of human DNA polymerase lambda (pol lambda), and compound 5 (3,5-dimethyl-8-methoxy-3,4-dihydroisocoumarin) was the strongest inhibitor of pol lambda in the tested compounds with an IC(50) value of 49 microM. New tetralols (1 and 2) are the third and second strongest inhibitors of pol lambda, but did not influence the activities of mammalian pols alpha to kappa, and showed no effect even on the activities of plant pols alpha and beta, 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.

Beta-sitosterol-3-O-beta-D-glucopyranoside: a eukaryotic DNA polymerase lambda inhibitor

Beta-sitosterol-3-O-beta-D-glucopyranoside (compound 1), a steroidal glycoside isolated from onion (Allium cepa L.) selectively inhibited the activity of mammalian DNA polymerase lambda (pol lambda) in vitro. The compound did not influence the activities of replicative DNA polymerases such as alpha, delta and epsilon, but also showed no effect even on the activity of pol beta which is thought to have a very similar three-dimensional structure to the pol beta-like region of pol lambda. Since parts of compound 1 such as beta-sitosterol (compound 2) and D-glucose (compound 3) did not influence the activities of any enzymes tested, the converted structure of compounds 2 and 3 might be important for pol lambda inhibition. The inhibitory effect of compound 1 on both intact pol lambda (i.e. residues 1-575) and a truncated pol lambda lacking the N-terminal BRCA1 C-terminus (BRCT) domain (133-575, del-1 pol lambda) was dose-dependent, and 50% inhibition was observed at a concentration of 9.1 and 5.4 microM, respectively. The compound 1-induced inhibition of del-1 pol lambda activity was non-competitive with respect to both the DNA template-primer and the dNTP substrate. On the basis of these results, the pol lambda inhibitory mechanism of compound 1 is discussed.

Structural relationship of curcumin derivatives binding to the BRCT domain of human DNA polymerase lambda

We previously reported that phenolic compounds, petasiphenol and curcumin (diferuloylmethane), were a selective inhibitor of DNA polymerase lambda (pol lambda) in vitro. The purpose of this study was to investigate the molecular structural relationship of curcumin and 13 chemically synthesized derivatives of curcumin. The inhibitory effect on pol lambda (full-length, i.e. intact pol lambda including the BRCA1 C- terminal [BRCT] domain) by some derivatives was stronger than that by curcumin, and monoacetylcurcumin (compound 13) was the strongest pol lambda inhibitor of all the compounds tested, achieving 50% inhibition at a concentration of 3.9 microm. The compound did not influence the activities of replicative pols such as alpha, delta, and epsilon. It had no effect on pol beta activity either, although the three-dimensional structure of pol beta is thought to be highly similar to that of pol lambda. Compound 13 did not inhibit the activity of the C-terminal catalytic domain of pol lambda including the pol beta-like core, in which the BRCT motif was deleted from its N-terminal region. MALDI-TOF MS analysis demonstrated that compound 13 bound selectively to the N-terminal domain of pol lambda, but did not bind to the C-terminal region. Based on these results, the pol lambda-inhibitory mechanism of compound 13 is discussed.

5-(Hydroxymethyl)-2-furfural: a selective inhibitor of DNA polymerase lambda and terminal deoxynucleotidyltransferase

5-(Hydroxymethyl)-2-furfural (HMF), a pyrolysate of carbohydrate isolated from instant coffee (Coffea arabica L.), selectively inhibits the activities of mammalian DNA polymerase lambda (pol lambda) and terminal deoxynucleotidyltransferase (TdT) which are family X pols, in vitro. The compound influenced neither the activities of replicative DNA polymerases such as alpha, delta, and epsilon, nor even the activity of pol beta which is from the same family and thought to have a very similar three-dimensional structure to the pol beta-like region of pol lambda. Since parts of HMF such as furan, furfuryl alcohol, and 2-furaldehyde did not influence the activities of any enzymes tested, the substituted form of furan with a hyroxymethyl group and a formyl group might be important for the inhibition of pol lambda and TdT. The inhibitory effect of HMF on intact pol lambda (i.e., residues 1-575), a truncated pol lambda lacking the N-terminal BRCA1 C-terminus domain (133-575, del-1 pol lambda) and another truncated pol lambda lacking the N-terminal proline-rich region (245-575, del-2 pol lambda) was dose-dependent, and 50% inhibition was observed at a concentration of 26.1, 10.3, and 4.6 microM, respectively. The IC(50) value of HMF for TdT was the same as that for del-2 pol lambda (5.5 microM). The HMF-induced inhibition of both pol lambda and TdT activities was competitive with respect to both the DNA template-primer and the dNTP substrate. On the basis of these results, HMF was suggested to bind to the pol beta-like region of pol lambda and TdT.