Transcription occurs at a nucleoskeleton

Abstract

Native chromatin aggregates under isotonic conditions so it is generally studied using higher or lower salt concentrations. This has led to different interpretations of how transcription might occur. Studies using hypertonically-isolated preparations suggest that DNA functions in close association with a skeletal nuclear substructure, the matrix or cage, but such a structure is not usually seen under hypotonic conditions (e.g., in 'Miller-spreads'). Using a novel method for preparing chromatin under isotonic conditions we have investigated the site of transcription. We find that all three constituents of the transcription complex, nascent transcripts, active RNA polymerase and genes being transcribed are all closely associated with some structure too large to be electroeluted from the nucleus. Hypotonic treatment partly disrupts this association. We suggest a model for transcription that involves the participation of a nucleoskeleton at the active site and reconcile the contradictory results obtained using different salt concentrations.