Post-transcriptional transfer of gamma-thio affinity label to RNA in isolated parsley nuclei

As an alternative to soluble plant transcription systems, we examined the reinitiation capacity of isolated parsley nuclei. Nuclear chalcone synthase in vitro transcripts were affinity-labelled with gamma-thio-ATP, gamma-thio-GTP or beta-thio-ATP, and purified by chromatography on a mercury Sepharose affinity column. Primer extension and subsequent PCR amplification of these in vitro transcripts revealed gamma-thio-ATP-dependent, but no beta-thio-ATP-dependent, signals, although affinity labelling of overall in vitro transcripts still occurred with beta-thio-ATP. We conclude that the described plant nuclei reinitiated transcription non-specifically and that post-transcriptional transfer of the gamma-thio affinity label severely interfered with the detection of reinitiated transcripts.