Nowadays, it has been demonstrated that DNA G-quadruplex arrangements are involved in cellular aging and cancer, thus boosting the discovery of selective binders for these DNA secondary structures. By taking advantage of available structural and biological information on these structures, we performed a high throughput in silico screening of commercially available molecules databases by merging ligand- and structure-based approaches by means of docking experiments. Compounds selected by the virtual screening procedure were then tested for their ability to interact with the human telomeric G-quadruplex folding by circular dichroism, fluorescence spectroscopy, and photodynamic techniques. Interestingly, our screening succeeded in retrieving a new promising scaffold for G-quadruplex binders characterized by a psoralen moiety.

Acetylation is a key modulator of genome accessibility through decondensation of the chromatin structure. The balance between acetylation and opposite deacetylation is, in fact, a prerequisite for several cell functions and differentiation. To find modulators of the histone acetyltransferase Gcn5p, we performed a phenotypic screening on a set of newly synthesized molecules derived from thiazole in budding yeast Saccharomyces cerevisiae. We selected compounds that induce growth inhibition in yeast strains deleted in genes encoding known histone acetyltransferases. A novel molecule CPTH2, cyclopentylidene-[4-(4'-chlorophenyl)thiazol-2-yl)hydrazone, was selected based on its inhibitory effect on the growth of a gcn5Delta strain. We demonstrated a specific chemical-genetic interaction between CPTH2 and HAT Gcn5p, indicating that CPTH2 inhibits the Gcn5p dependent functional network. CPTH2 inhibited an in vitro HAT reaction, which is reverted by increasing concentration of histone H3. In vivo, it decreased acetylation of bulk histone H3 at the specific H3-AcK14 site. On the whole, our results demonstrate that CPTH2 is a novel HAT inhibitor modulating Gcn5p network in vitro and in vivo.

A series of 2-methylcyclohexylidene-(4-arylthiazol-2-yl)hydrazones have been investigated for their ability to inhibit selectively the activity of the human A and B isoforms of monoamine oxidase (MAO). The target compounds, which present a stereogenic center on the cyclohexane ring, were obtained as pure (R) and (S) enantiomers by enantioselective HPLC. The absolute configuration of homochiral forms isolated on a semipreparative scale was obtained by a combined strategy based on chemical correlation and single-crystal X-ray diffraction. All compounds showed higher activity against the human MAO-B isoform with IC50 values ranging between 26.81 +/- 2.74 microM and 14.20 +/- 0.26 nM, and the assays carried out on the pure enantiomers showed higher activity for the (R) form. A computational study was performed by molecular mechanics, DFT-based quantomechanics, and docking techniques on the most active and human MAO-B selective inhibitor 8.

The DNA polymerase and ribonuclease H (RNase H) activities of human immunodeficiency virus type 1 (HIV-1) are needed for the replication of the viral genome and are validated drug targets. However, there are no approved drugs inhibiting RNase H and the efficiency of DNA polymerase inhibitors can be diminished by the presence of drug resistance mutations. In this context, drugs inhibiting both activities could represent a significant advance towards better anti-HIV therapies. We report on the mechanisms of allosteric inhibition of a newly synthesized isatin-based compound designated as RMNC6 that showed IC50 values of 1.4 and 9.8 μM on HIV-1 RT-associated RNase H and polymerase activities, respectively. Blind docking studies predict that RMNC6 could bind two different pockets in the RT: one in the DNA polymerase domain (partially overlapping the non-nucleoside RT inhibitor [NNRTI] binding pocket), and a second one close to the RNase H active site. Enzymatic studies showed that RMNC6 interferes with efavirenz (an approved NNRTI) in its binding to the RT polymerase domain, although NNRTI resistance-associated mutations such as K103N, Y181C and Y188L had a minor impact on RT susceptibility to RMNC6. In addition, despite being naturally resistant to NNRTIs, the polymerase activity of HIV-1 group O RT was efficiently inhibited by RMNC6. The compound was also an inhibitor of the RNase H activity of wild-type HIV-1 group O RT, although we observed a 6.5-fold increase in the IC50 in comparison with the prototypic HIV-1 group M subtype B enzyme. Mutagenesis studies showed that RT RNase H domain residues Asn474 and Tyr501, and in a lesser extent Ala502 and Ala508, are critical for RMNC6 inhibition of the endonuclease activity of the RT, without affecting its DNA polymerization activity. Our results show that RMNC6 acts as a dual inhibitor with allosteric sites in the DNA polymerase and the RNase H domains of HIV-1 RT.

A novel series of 1-thiocarbamoyl-3,5-diaryl-4,5-dihydro-(1H)-pyrazole derivatives have been synthesized and investigated for the ability to inhibit selectively the activity of the A and B isoforms of monoamine oxidase (MAO). All the synthesized compounds show high activity against both the MAO-A and the MAO-B isoforms with Ki values between 27 and 4 nM and between 50 and 1.5 nM, respectively, except for a few derivatives whose inhibitory activity against MAO-B was in the micromolar range. Knowing that stereochemistry may be an important modulator of biological activity, we performed the semipreparative chromatographic enantioseparation of the most potent, selective, and chiral compounds. The separated enantiomers were then submitted to in vitro biological evaluation. The selectivity of the (-)-(S)-1 enantiomer against MAO-B increases twice and a half, while the selectivity of the (-)-(S)-4 enantiomer against MAO-A triples. Both the MAO-A and MAO-B isoforms respectively of the 1O5W and 1GOS models deposited in the Protein Data Bank were considered in the computational study. The docking study was carried out using several computational approaches with the aim of proposing possible binding modes of the MAO enantioselective compounds 1 and 4.

A series of 2-thiazolylhydrazone derivatives have been investigated for the ability to inhibit the activity of the A and B isoforms of monoamine oxidase (MAO) selectively. All of the compounds showed high activity against both the MAO-A and the MAO-B isoforms with pKi values ranging between 5.92 and 8.14 for the MAO-A and between 4.69 and 9.09 for the MAO-B isoforms. Both the MAO-A and the MAO-B isoforms, deposited in the Protein Data Bank as model 2BXR and 1GOS, respectively, were considered in a computational study performed with docking techniques on the most active and MAO-B-selective inhibitor, 18.

No abstract

SSAO/VAP-1 is not only involved in the metabolism of biogenic and xenobiotic primary amines and in the production of metabolites with cytotoxic effects or certain physiological actions, but also plays a role, for example, as an adhesion molecule, in leukocyte trafficking, in regulating glucose uptake and in adipocyte homeostasis. Interest in the enzyme has been stimulated by the findings that the activities of the SSAOs are altered (mostly increased) in various human disorders, including diabetes, congestive heart failure, liver cirrhosis, Alzheimer's disease and several inflammatory diseases, although the underlying causes are often unknown. On the basis of their insulin-mimicking effect, SSAO substrates are possibly capable of ameliorating metabolic changes in diabetes, while SSAO inhibitors (somewhat of a contradiction) are of potential benefit in preventing diabetes complications, atherosclerosis and oxidative stress contributing to several disorders or modulating inflammation, and hence may be of substantial therapeutic value. Great efforts have been made to develop novel compounds which may lead to future drugs useful in therapy, based on their effects on SSAO/VAP-1, and some of the results relating to novel substrates and inhibitors are surveyed in the present review.