The effects of DNA intercalators on chromatin of chicken red blood cells---differential extraction on nonhistone proteins

Taking advantage of the effects on DNA secondary structure of two DNA-intercalators,ethidium bromide and chloroquine,we used each of them to treat nuclei from both mature erythrocytes and reticulocytes of chicken,as an alternative approach to study the relationships between DNA secondary structure,nuclear proteins and chromatin structure.We presented results of differential extraction of nuclear proteins from nuclei with DNA-intercalators,as well as preliminary characterization of these proteins.A 45kd protein is the major component in fractions extracted by both intercalators from nuclei from either mature erythrocytes or reticulocytes and seems to be a DNA-binding protein.Furthermore,from current concepts of functional aspects of DNA conformation and structural heterogeneity in chromatin and nuclear proteins,we have discussed both the significance of our results as well as technical aspects of this approach.

Characterization of DNA Intercalator Bound to Calf Thymus DNA:Ionic Strength and pH Value Effects

By means of circular dichroism（CD） spectrum coupled with UV-Vis and fluorescence spectra,the binding model of DNA intercalator A1{4-（2-diethylamino-ethylamino）-8-oxo-8H-acenaphtho[1,2-b]pyrrole-9-carbonitrile} to calf thymus（CT） DNA was investigated,depending on the values of R（R is defined as the ratio of the concentration of A1 to CT DNA base pairs） and different outer factors.Molecules A1 were intercalated into the CT DNA base pairs in different orientations in the intercalation pocket at a lower R value（R≤0.20）,while A1 molecules aggregated on the surface of the helix of the CT DNA as the R value increased.The influence of NaCl on the binding was smaller because the electrostatic interaction only provided approximately 16% of the overall free energy of binding.The protonated diethylamine substitution would influence the binding geometry greatly at a low pH value via forming hydrogen bonds with the exposed C=O group on DNA surface.

Inhibition of protein kinases by anticancer DNA intercalator, 4-butylaminopyrimido[4',5':4,5]thieno(2,3-b)quinoline

Targeting protein kinases(PKs) has been a promising strategy in treating cancer, as PKs are key regulators of cell survival and proliferation. Here in this study, we studied the ability of pyrimido[4',5':4,5]thieno(2,3-b)quinolines(PTQ) to inhibit different PKs by performing computational docking and in vitro screening. Docking studies revealed that 4-butylaminopyrimido[4',5':4,5]thieno(2,3-b)quinoline(BPTQ) has a higher order of interaction with the kinase receptors than other PTQ derivatives.In vitro screening confirms that BPTQ inhibits VEGFR1 and CHK2, with the IC_(50) values of 0.54 and1.70 mmol/L, respectively. Further, cytotoxicity of BPTQ was measured by trypan blue assay. Treatment with BPTQ decreased the proliferation of HL-60 cells with an IC_(50) value of 12 mmol/L and induces apoptosis, as explicated by the fall in the mitochondrial membrane potential, annexin V labeling and increased expression of caspase-3. Taken together, these data suggest that BPTQ possess ability to inhibit PKs and to induce cell death in human promyelocytic leukemia cells.

Targeted genome mining for microbial antitumor agents acting through DNA intercalation

Microbial natural products have been one of the most important sources for drug development.In the current postgenomic era,sequence-driven approaches for natural product discovery are becoming increasingly popular.Here,we develop an effective genome mining strategy for the targeted discovery of microbial metabolites with antitumor activities.Our method employs uvrA-like genes as genetic markers,which have been identified in the biosynthetic gene clusters(BGCs)of several chemotherapeutic drugs of microbial origin and confer self-resistance to the corresponding producers.Through systematic genomic analysis of gifted actinobacteria genera,identification of uvrA-like gene-containing BGCs,and targeted isolation of products from a BGC prioritized for metabolic analysis,we identified a new tetracycline-type DNA intercalator timmycins.Our results thus provide a new genome mining strategy for the efficient discovery of antitumor agents acting through DNA intercalation.