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Nucleic Acids Research Nov 1987Oligo-heptathymidylates covalently linked to porphyrins bind to complementary sequences and can induce local damages on the target molecule. In dark reactions, iron...
Oligo-heptathymidylates covalently linked to porphyrins bind to complementary sequences and can induce local damages on the target molecule. In dark reactions, iron porphyrin derivatives exhibited various chemical reactivities resulting in base oxidation, crosslinking and chain scission reactions. Reactions induced by reductants, such as ascorbic acid, dithiothreitol or mercapto-propionic acid, led to very localised reactions. A single base was the target for more than 50% of the damages. Oxidising agents such as H2O2 and its alkyl derivatives induced reactions that extended to a wider range of altered bases. The specificity of the chemical modifications observed in these systems is discussed from a mechanistic point of view.
Topics: Alkylating Agents; Aminacrine; Ascorbic Acid; Cross-Linking Reagents; DNA Damage; Dithiothreitol; Hydrogen Peroxide; Metalloporphyrins; NAD; Oxidation-Reduction; Poly T; Polydeoxyribonucleotides; Sulfhydryl Compounds
PubMed: 3684568
DOI: 10.1093/nar/15.21.8643 -
Nucleic Acids Research Aug 1987The DNA unwinding effects of some 9-aminoacridine derivatives were compared under reaction conditions that could be used to study drug-induced topoisomerase II... (Comparative Study)
Comparative Study
The DNA unwinding effects of some 9-aminoacridine derivatives were compared under reaction conditions that could be used to study drug-induced topoisomerase II inhibition. An assay was designed to determine drug-induced DNA unwinding by using L1210 topoisomerase I. 9-aminoacridines could be ranked by decreasing unwinding potency: compound C greater than or equal to 9-aminoacridine greater than o-AMSA greater than or equal to compound A greater than compound B greater than m-AMSA. Ethidium bromide was more potent than any of the 9-aminoacridines. This assay is a fast and simple method to compare DNA unwinding effects of intercalators. It led to the definition of a drug intrinsic unwinding constant (k). An additional finding was that all 9-aminoacridines and ethidium bromide inhibited L1210 topoisomerase I. Enzyme inhibition was detectable at low enzyme concentrations (less than or equal to 1 unit) and when the kinetics of topoisomerase I-mediated DNA relaxation was studied. Topoisomerase I inhibition was not associated with DNA swivelling or cleavage.
Topics: Aminacrine; Aminoacridines; Animals; DNA, Viral; Ethidium; Intercalating Agents; Leukemia L1210; Mice; Neoplasm Proteins; Nucleic Acid Conformation; Structure-Activity Relationship; Topoisomerase I Inhibitors
PubMed: 2819825
DOI: 10.1093/nar/15.16.6713 -
Proceedings of the National Academy of... Aug 1987The neighbor-exclusion principle is one of the most general and interesting rules describing intercalative DNA binding by small molecules. It suggests that such binding...
Molecular mechanical simulations on double intercalation of 9-amino acridine into d(CGCGCGC) X d(GCGCGCG): analysis of the physical basis for the neighbor-exclusion principle.
The neighbor-exclusion principle is one of the most general and interesting rules describing intercalative DNA binding by small molecules. It suggests that such binding can only occur at every other base-pair site, reflecting a very large negative cooperativity in the binding process. We have carried out molecular mechanics and molecular dynamics simulations to study intercalation complexes between 9-amino acridine and the base-paired heptanucleotide d(CGCGCGC) X d(GCGCGCG), in which the neighbor-exclusion principle was both obeyed and violated. Our studies find no stereochemical preference that favors the neighbor-exclusion-obeying structures over the neighbor-exclusion-violating structures. Alternative explanations for the existence of the neighbor-exclusion principle are vibrational entropy effects that we calculate to favor the more flexible neighbor-exclusion models over the more rigid neighbor-exclusion-violating models and polyelectrolyte (counterion release) effects.
Topics: Aminacrine; Aminoacridines; Models, Molecular; Nucleic Acid Conformation; Polydeoxyribonucleotides
PubMed: 3475700
DOI: 10.1073/pnas.84.16.5735 -
Nucleic Acids Research Jun 1987The effects of anti-messenger oligodeoxynucleotides, covalently linked to an intercalating agent, on translation of rabbit beta-globin mRNA, were investigated both in...
The effects of anti-messenger oligodeoxynucleotides, covalently linked to an intercalating agent, on translation of rabbit beta-globin mRNA, were investigated both in wheat germ extract and in microinjected Xenopus oocytes. A specific inhibition of beta-globin synthesis was observed in both expression systems with a modified 11-mer covalently linked to an acridine derivative. In injected oocytes a more efficient block was observed with this modified oligonucleotide than with its unsubstituted homolog. This was ascribed to stacking interactions of the intercalating agent with base pairs which provide an additional stabilization of the [mRNA/DNA] hybrid. We demonstrated that in wheat germ extract, the modified and unmodified oligonucleotides behaved similarly due to the presence of a high RNaseH activity. RNaseH was also present, although to a lesser extent, in the oocyte cytoplasm. This anti-messenger DNA-induced degradation of target mRNA resulted in amplified efficiency of hybrid-arrested translation. This additional mechanism might provide anti-sense DNAs with an advantage over anti-sense RNAs.
Topics: Aminacrine; Animals; Cell-Free System; DNA; Depression, Chemical; Endoribonucleases; Female; Globins; Intercalating Agents; Nucleic Acid Hybridization; Oligodeoxyribonucleotides; Oocytes; Protein Biosynthesis; RNA, Messenger; Rabbits; Ribonuclease H; Triticum; Xenopus
PubMed: 3037483
DOI: 10.1093/nar/15.12.4717 -
The Journal of Biological Chemistry May 1987A demonstration is made of pyrophosphate's use as a precipitating anion in studies of Ca2+ release from isolated sarcoplasmic reticulum (SR). Not only does pyrophosphate...
A demonstration is made of pyrophosphate's use as a precipitating anion in studies of Ca2+ release from isolated sarcoplasmic reticulum (SR). Not only does pyrophosphate speed up the rate at which Ca2+ can be preloaded into SR, but it also allows the accumulated Ca2+ to be released in response to agents such as caffeine. Because so much Ca2+ can be preloaded into SR with pyrophosphate present, more experiments can be performed with a given amount of SR material, and even rapid Ca2+ release rates (greater than 1 mumol/mg X min) are maintained for many seconds. These rates can easily be quantified using conventional spectrophotometric and isotopic methods, without the need for expensive rapid mixing equipment. Caffeine-induced Ca2+ release is exhibited by triadic and terminal cisterna SR subfractions but not by light SR. Caffeine specifically increases the rate of unidirectional 45Ca2+ efflux. This increased efflux is blocked by ruthenium red at submicromolar concentrations and by tetracaine, 9-aminoacridine, or Ba2+ at submillimolar concentrations.
Topics: Aminacrine; Animals; Barium; Caffeine; Calcium; Diphosphates; Fluorides; Oxalates; Oxalic Acid; Rabbits; Ruthenium Red; Sarcoplasmic Reticulum; Tetracaine
PubMed: 2437114
DOI: No ID Found -
British Journal of Cancer Jan 1987Fluorescence probes for the active centre of an enzyme associated with tumour cells have been used to locate leukaemia cells in a model rat system. These fluorescent...
Fluorescence probes for the active centre of an enzyme associated with tumour cells have been used to locate leukaemia cells in a model rat system. These fluorescent techniques are inexpensive and rapid to carry out. The leukaemic cells can be located by fluorescence microscopy in frozen sections, wax embedded sections and resin embedded sections. The technique is illustrated with reference to sections of leukaemic rat kidney, epididymis and testis. These studies confirm earlier histological findings employing conventional staining techniques and have the advantage that individual leukaemia cells can be detected in leukaemic animals undergoing drug therapy. The evidence suggests that these techniques will be of value in further studies of the design of drugs directed to leukaemia cells.
Topics: Aminacrine; Animals; Epididymis; Fluorescent Dyes; Kidney Neoplasms; Leukemia, Experimental; Lymphocytes; Male; Propidium; Rats; Rats, Inbred Strains; Remission Induction; Testicular Neoplasms; Tosyllysine Chloromethyl Ketone
PubMed: 3814472
DOI: 10.1038/bjc.1987.6 -
Journal of Leukocyte Biology Jan 1987We have previously reported that human neutrophils can be permeabilized with the cholesterol-complexing agent digitonin. These permeabilized cells can be induced to...
We have previously reported that human neutrophils can be permeabilized with the cholesterol-complexing agent digitonin. These permeabilized cells can be induced to secrete lysosomal constituents when exposed to micromolar levels of free Ca2+, a process that is enhanced by certain guanine nucleotides. We examined the kinetics in this system by employing both direct and indirect measures of secretion. A continuous, fluorescent assay of elastase permits real-time monitoring of secretion from azurophil granules. The kinetics of elastase release proved to be rapid, beginning within 3-10 sec and reaching a maximum at 1-2 min. Changes in the Ca2+ concentration did not affect the "lag period" for release. A comparison of the Ca2+ dose-response curves for release of the various granule constituents indicated that elastase was being secreted along with other contents of the azurophil granules. Changes in right angle light scatter (RLS), which have been shown to correlate closely with secretion, also commenced rapidly after the addition of Ca2+; when measured simultaneously, both the Ca2+ dose-response characteristics for changes in RLS and elastase release were very similar. Changes in RLS could be halted within 5 sec by excess EGTA and restarted promptly by repletion with secretory concentrations of Ca2+. In addition, neomycin, a phospholipase C inhibitor, profoundly diminished degranulation as monitored by RLS and end-point techniques. A continuous assay employing 9-aminoacridine self-quenching as a measure of secretion proved far less satisfactory, but, nonetheless, produced similar kinetics and dose-response characteristics.(ABSTRACT TRUNCATED AT 250 WORDS)
Topics: Aminacrine; Calcium; Cells, Cultured; Dose-Response Relationship, Drug; Humans; Kinetics; Light; Neomycin; Neutrophils; Pancreatic Elastase; Permeability; Scattering, Radiation
PubMed: 3468190
DOI: 10.1002/jlb.41.1.8 -
The Journal of Biological Chemistry Dec 1986The ability of 9-aminoacridine to induce mutagenic lesions during DNA replication in vitro was investigated. The ampicillinase gene of pBR322 was replicated in vitro in...
The ability of 9-aminoacridine to induce mutagenic lesions during DNA replication in vitro was investigated. The ampicillinase gene of pBR322 was replicated in vitro in the presence of 9-aminoacridine. Transfection of the replicated DNA into Escherichia coli gave Amps mutants. Determination of the base changes in 76 of these mutants indicated that the spectrum of mutations induced by 9-aminoacridine was consistent with its action in vivo. Both large (407-base) and small (1- and 2-base) deletions were induced at repetitive sequences. The frequency of deletion mutations depended on the identity of the base deleted and sequences surrounding the deletions. The characteristics of the frameshift mutations induced were consistent with the interactions of 9-aminoacridine with DNA. These results establish that 9-aminoacridine can induce frameshift mutations during the replication process and provide an in vitro model of frameshift induction for mechanistic studies.
Topics: Aminacrine; Aminoacridines; Base Sequence; Chromosome Deletion; DNA; DNA Replication; In Vitro Techniques; Mutation
PubMed: 3782116
DOI: No ID Found -
Proceedings of the National Academy of... Sep 1986Frameshift mutations were induced by proflavin in the rIIB gene of bacteriophage T4. rIIB DNA from each of 48 independent frameshifts was inserted into M13mp8 and...
Frameshift mutations were induced by proflavin in the rIIB gene of bacteriophage T4. rIIB DNA from each of 48 independent frameshifts was inserted into M13mp8 and sequenced. Two-thirds of the frameshifts (33/48) lie contiguous to one another in 10 base pairs of the rIIB sequence. This hotspot differs markedly from previously characterized mutagen-induced frameshift hotspots. Distinctive features of the hotspot include the absence of locally repetitive sequences, particularly G X C runs, and the fact that many different sequence changes are induced within the hotspot sequence at appreciable frequencies. Among the 33 mutants at the hotspot, 8 distinguishable DNA sequence changes were seen. All of the mutations were deletions of a single base or duplications of one or more bases. Duplications were more frequent than deletions. The patterns of the base sequence changes suggest that two specific phosphodiester bonds within the hotspot sequence are sites at which proflavin-induced mutation is initiated.
Topics: Acridines; Aminacrine; Aminoacridines; Base Sequence; DNA, Viral; Mutagens; Mutation; Nitrogen Mustard Compounds; Proflavine; T-Phages
PubMed: 3462738
DOI: 10.1073/pnas.83.18.6954 -
Journal of Bacteriology Jul 1986A mutant of Salmonella typhimurium LT2 deficient in methylation of the adenine residues in the sequence 5'-GATC-3' was isolated. The mutation (dam-1) was linked to the...
A mutant of Salmonella typhimurium LT2 deficient in methylation of the adenine residues in the sequence 5'-GATC-3' was isolated. The mutation (dam-1) was linked to the cysG locus, and the properties of the mutant were similar to those of Escherichia coli dam mutants. Reversion of the hisC3076 frameshift marker by 9-aminoacridine was substantially enhanced by the dam-1 mutation, implying a direct role for adenine methylation in the prevention of frameshift mutation induction.
Topics: Adenine; Aminacrine; DNA, Bacterial; Genes, Bacterial; Methylation; Methyltransferases; Mutation; Salmonella typhimurium; Site-Specific DNA-Methyltransferase (Adenine-Specific)
PubMed: 3522556
DOI: 10.1128/jb.167.1.420-422.1986