TRANSCRIPTION OF INVITRO ASSEMBLED CHROMATIN BY ESCHERICHIA-COLI RNA-POLYMERASE

In vitro assembled chromatin was prepared from simian virus 40 DNA form I and the four calf thymus histones H2a, H2b, H3 and H4. Transcription of this template by Escherichia coli RNA polymerase holoenzyme was inhibited at the level of initiation and elongation; no preferential termination was observed. The inhibition of both initiation and elongation depended on the number of nucleosomes in the reconstituted complexes. It was found that RNA polymerase could elongate RNA chains across regions of the DNA occupied by nucleosomes. Elongation was greatly facilitated at increased ionic strength. At these salt concentrations no exchange or sliding of histone core particles was observed. © 1979.