RNA synthesis: a requirement for hormone-induced DNA amplification in Rhynchosciara americana.
Injection of beta-ecdysone into mid fourth instar larvae of Rhynchosciara americana induced within 23-28 hours after injection a rise in the percentage of 3H-thymidine (3H-TdR) incorporating nuclei in salivary gland region S1 from about 10-20% in the controls to 80-90% in the injected larvae. The 3H-TdR incorporating nuclei displayed a weak continuous labeling pattern or a band-labeling pattern with grains over the vast majority of the bands. The majority of nuclei with a band labeling pattern displayed DNA amplification at the DNA-puff regions.--Injection of actinomycin D at different times after ecdysone injection abolished the higher incorporation rate at the amplifying regions within 15 hours after the injection. However, the percentage of nuclei incorporating 3H-TdR and the frequency of the two labeling patterns remained essentially the same when RNA synthesis was inhibited. Only the over-all rate of 3H-TdR incorporation seemed to be reduced.--These data suggest that in the DNA puff regions the rate of DNA chain elongation is higher when amplification occurs than during a normal replication cycle. It, further, seems that the higher rate during amplification is dependent upon de novo RNA synthesis.
D000818:Animals; D001345:Autoradiography; D002875:Chromosomes / Q000187:drug effects / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects; D003609:Dactinomycin / Q000494:pharmacology; D004175:Diptera / Q000166:cytology* / Q000254:growth & development; D004440:Ecdysone / Q000494:pharmacology*; D005260:Female; D005796:Genes; D007814:Larva; D012313:RNA / Q000096:biosynthesis*; D012469:Salivary Glands / Q000166:cytology; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors; D014316:Tritium
D014316:Tritium; D003609:Dactinomycin; D004440:Ecdysone; D012313:RNA; D013936:Thymidine