Unusual RNA polymerase content of Trypanosoma brucei nuclei.

Nuclei were isolated from bloodstream forms of Trypanosoma brucei by nitrogen cavitation and sedimentation through percoll density gradients. Transcription studies with these nuclei in vitro demonstrated features not seen with other eukaryotes: RNA synthesis was much greater in the presence of Mn2+ than with Mg2+ and was sensitive to high concentrations (10-100 micrograms/ml) of alpha-amanitin at all salt concentrations tested (25-300 mM ammonium sulphate). RNA polymerase extracted from nuclei by sonication at high ionic strength chromatographed as a single peak, sensitive to high alpha-amanitin concentrations, on DEAE-sephadex under conditions which resolved the classic three RNA polymerase forms when rat liver nuclear extracts were used.