title: Small circular DNA in Drosophila melanogaster.
abstract: Covalently closed small circular DNA isolated from Drosophila melanogaster is described. The small circular DNA is found in blastema stage eggs and in Schneider's cell culture line 2 and a cloned subline of line 2. It is heterogeneous in size, although the size distributions and mean sizes differ for each source. The small circular DNA from Schneider's line 2 cells ranges from 0.09-7.3 mum, with a mean contour length of 1.1 mum. This DNA has a buoyant density of 1.703 g/cc and appears to be present predominantly in the nuclear fraction of detergent-disrupted cells. the restriction enzyme EcoRl cleaves approximately 40% of the small circular DNA with a bias toward the larger size classes. Both logarithmic and stationary phase cells contain approximately 3-40 average sized small circular DNA molecules per cell, representing a maximum of 0.03% of the total cellular DNA. Exposure to cycloheximide or puromycin for 14 hr results in a 30 fold increase in the number of small circles per cell, but reduces the mean length of the circular DNA to 0.3 mum. The drug-amplified DNA has a buoyant density in the range of 1.698-1.703 g/cc. No amplification was seen in cells treated with either inhibitor for 3.5 hr. Ethidium bromide, cytosine arabinoside, beta-ecdysone, and insulin all had no significant effect on the amount per cell of either small circular DNA or mitochondrial DNA.
mesh_terms: D000818:Animals; D002460:Cell Line; D002467:Cell Nucleus / Q000032:analysis; D002499:Centrifugation, Density Gradient; D003513:Cycloheximide / Q000494:pharmacology; D003561:Cytarabine / Q000494:pharmacology; D003593:Cytoplasm / Q000032:analysis; D004261:DNA Replication / Q000187:drug effects; D004262:DNA Restriction Enzymes; D004270:DNA, Circular; D004331:Drosophila melanogaster; D004996:Ethidium / Q000494:pharmacology; D005260:Female; D007328:Insulin / Q000494:pharmacology; D007621:Karyotyping; D009690:Nucleic Acid Conformation; D010063:Ovum / Q000032:analysis; D011691:Puromycin / Q000494:pharmacology
chemical_list: D004270:DNA, Circular; D007328:Insulin; D003561:Cytarabine; D011691:Puromycin; D003513:Cycloheximide; D004262:DNA Restriction Enzymes; D004996:Ethidium