[Fluorescence microscopic and autoradiographic analyses of the differential reaction of various regions of polytene chromosomes in Chironomus to prolonged exposure to 7-amino-actinomycin D and 3H-actinomycin D].
Dynamics of binding of a fluorescent analogue of actinomycin D -- 7-amino-actinomycin D -- and 3H-actinomycin D with polytene chromosomes of Ch. thummi was studied. Biological effects of AMD, 7-amino-AMD, and 3H-AMD on polytene chromosomes were found to be similar. These ligands provoke the reduction of the nucleolus and Balbiani rings and the appearance of giant pseudo-puffs in heterochromatic centromere regions of polytene chromosomes. There was no intermediate binding of 7-amino-AMD to DNA in vivo both after a longterm treatment of larvae with fluorochrome and in chase experiments. It was found that a loosening of chromatin in centromere regions accompanied by a weakening of its fluorescence took place in the formation of pseudo-puffs. Possible mechanisms of pseudo-puff formation under the influence of AMD and 7-amino-AMD are discussed. Essential factors may be peculiarities of DNA nucleotide composition in centromere regions, DNA packing, alteration of physico-chemical properties of DNA in the complex with AMD (despiralizations and elongation), and an inhibition of RNA synthesis necessary for the maintenance of normal structure of polytene chromosomes.
D000818:Animals; D001345:Autoradiography; D002683:Chironomidae / Q000187:drug effects* / Q000235:genetics; D002875:Chromosomes / Q000187:drug effects* / Q000648:ultrastructure; D003609:Dactinomycin / Q000031:analogs & derivatives* / Q000494:pharmacology*; D004175:Diptera / Q000187:drug effects*; D007814:Larva / Q000187:drug effects; D008856:Microscopy, Fluorescence; D013997:Time Factors; D014316:Tritium
D014316:Tritium; D003609:Dactinomycin; C025942:7-aminoactinomycin D
Fluorestsentno-mikroskopicheskiĭ i avtoradiograficheskiĭ analizy differentsial'noĭ reaktsii razlichnykh uchastkov politennykh khromosom khironomusa na dlitel'noe vozdeĭstvie 7-amino-aktinomitsina D i 3H-aktinomitsina D.