Transcription of histone-covered T7 DNA by Escherichia coli RNA polymerase

Purified core histones (H2A, H2B, H3, and H4) and bacteriophage T7 DNA have been reconstituted to form a nucleoprotein complex, and the properties of this complex as a template for transcription by Escherichia coli RNA polymerase have been studied. At low ionic strength, RNA chain elongation rates are slow, and the chains produced even after long incubation are short. At higher salt concentrations, chain-elongation rates approach those on naked DNA. Since the salt concentrations used are not in themselves sufficient to dissociate the histones from the DNA, some mechanism must exist that permits passage of the polymerase through histone-covered regions.