[Localisation of the α-amanitin-sensitive RNA-polymerase in nuclei of Acetabularia]

An isolation medium for nuclei of Acetabularia mediterranea is described. The medium offers the possibility to keep nuclei alive (verified by reimplantation) for at least 10 min and to obtain nuclei with radioactively labelled RNA.The influence of α-amanitin on nucleolar and nucleoplasmatic RNA-synthesis is investigated autoradiographically. Amanitin inhibits the incorporation of uridine into the nucleoplasmatic RNA, whereas incorporation into the RNA of nucleoli is hardly or not at all influenced.We conclude that, in agreement with findings on animal cells, α-amanitin inhibits at least one of the RNA-polymerases localized in the nucleoplasm but does not markedly influence the RNA-polymerase of the nucleoli.