title: More evidence for replication-transcription-coupling in Physarum polycephalum.
abstract: Endogenous RNA polymerase activity of isolated nuclei from Physarum polycephalum was determined at high (400 mM KCl) and low (5--100 mM KCl) ionic strength. The activity of RNA polymerase B (alpha-amanitin-sensitive UMP incorporation) and of RNA polymerase A (plus C) (alpha-amanitin-resistant UMP incorporation) was compared in accurately sized nuclear samples derived from macroplasmodia at distinct points of the mitotic cycle. Minimum total RNA polymerase activity was detected in metaphase nuclei. A constant level of RNA polymerase B activity was detected at all other stages of the mitotic cycle, if nuclei were assayed at high ionic strength. However, a high level in S-phase, a low level in G2-phase and again a high level in early prophase were measured, if nuclei were assayed at low ionic strength. Inhibition of DNA synthesis by hydroxyurea in vivo had a selective and drastic effect on in vitro RNA polymerase activity of isolated nuclei derived from S-phase plasmodia, yielding up to 100% inhibition in early S-phase.
mesh_terms: D002453:Cell Cycle; D002467:Cell Nucleus / Q000187:drug effects / Q000201:enzymology; D004261:DNA Replication / Q000187:drug effects; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D006918:Hydroxyurea / Q000494:pharmacology; D009994:Osmolar Concentration; D010804:Physarum / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D012321:DNA-Directed RNA Polymerases; D006918:Hydroxyurea