Some evidence for replication-transcription coupling in Physarum polycephalum.
Hydroxyurea, at concentrations of 40-60 mM, selectively and effectively blocked incorporation of thymidine into DNA. Inhibition occurred within 5-10 min of application of the agent when DNA synthesis was in progress, while the onset of replication at the beginning of S-phase and DNA synthesis in G2 phase were not affected. Uridine incorporation into TCA-precipitable material, in the presence of hydroxyurea, was significantly (up to 70%) inhibited in early S-phase of the cell cycle. Selective inhibition of RNA synthesis was confirmed for RNA separated into rRNA-rich and poly(A)-rich RNA fractions and analysed by the 2 kinds of DNA-RNA hybridization reactions. Uridine incorporation into poly (A) RNA was also inhibited under conditions where cycloheximide prevented maturation of nascent DNA molecules in early S-phase. We assume that chromatin which is replicating early DNA sequences may be a more competent template for transcription.
D002843:Chromatin / Q000032:analysis; D003513:Cycloheximide / Q000009:adverse effects; D004247:DNA / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D004261:DNA Replication / Q000187:drug effects*; D006824:Hybridization, Genetic; D006918:Hydroxyurea / Q000009:adverse effects*; D008938:Mitosis; D009235:Myxomycetes / Q000254:growth & development*; D010804:Physarum / Q000254:growth & development*; D012313:RNA / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D013698:Templates, Genetic; D013936:Thymidine / Q000378:metabolism*; D014158:Transcription, Genetic / Q000187:drug effects*; D014529:Uridine / Q000378:metabolism*
D002843:Chromatin; D012313:RNA; D004247:DNA; D003513:Cycloheximide; D013936:Thymidine; D014529:Uridine; D006918:Hydroxyurea