Synthesis of (+) and (-) RNA molecules of potato spindle tuber viroid (PSTV) in isolated nuclei and its impairment by transcription inhibitors.

Transcription studies with highly purified potato cell nuclei in combination with a 'transcription-hybridization analysis' unequivocally demonstrate that the nucleus is the subcellular site where the entire process of PSTV replication takes place. Inhibition experiments with actinomycin D and alpha-amanitin furthermore suggest that the nuclear DNA-dependent RNA polymerases I and II are involved in the synthesis of PSTV (+) and (-) RNA, respectively.