MECHANISM OF TRANSCRIPTION THROUGH THE NUCLEOSOME BY EUKARYOTIC RNA-POLYMERASE

Nucleosomes, the nucleohistone subunits of chromatin, are present on t ranscribed eukaryotic genes but do not prevent transcription. It is sh own here that the large yeast RNA polymerase III transcribes through a single nucleosome. This takes place through a direct internal nucleos ome transfer in which histones never leave the DNA template, During th is process, the polymerase pauses with a pronounced periodicity of 10 to 11 base pairs, which is consistent with restricted rotation in the DNA loop formed during transfer. Transcription through nucleosomes by the eukaryotic enzyme and by much smaller prokaryotic RNA polymerases thus shares many features, reflecting an important property of nucleos omes.