Identification of an inhibitor of transcription in extracts prepared from wheat shoot nuclei

The analysis of run-off transcripts initiated in vitro from the CaMV 35S promoter in a HeLa whole-cell extract was used to assay plant nuclei extracts for the presence of an inhibitor of transcription. Extracts of isolated wheat shoot nuclei contained an activity that inhibited transcription directed from the CaMV 35S promoter. The amount of inhibition was variable between each preparation of the wheat nuclei extract, and was labile to cold storage and heat denaturation. No inhibitory activity could be detected, using the same extraction procedure and assay conditions, in extracts prepared from turnip leaf nuclei. HeLa whole-cell extracts inhibit non-specific transcription in plant extracts