Studies on pulse-labelled RNA during the mitotic cycle of Physarum polycephalum by subnuclear fractionation.

A method is described for the isolation of pulse-labelled RNA from nuclei and subnuclear fractions of Physarum polycephalum. At all times during interphase the nucleolar RNA consisted mainly of a 34-S rRNA precursor with only small amounts of 26-S and 19-S rRNAs. The nucleoplasmic RNA consisted of predominantly mature 26-S rRNA with small amounts of 19-S rRNA and a 30-S RNA species. The 30-S RNA component displayed different labelling kinetics from the rRNA precursors. A low molecular weight RNA fraction (4-8 S) appeared to accumulate in the nucleus as interphase progressed.