Elongation by RNA polymerase II on chromatin templates requires topoisomerase activity.
Transcription on chromatin by RNA polymerase II (pol II) is repressed as compared with transcription on histone-free DNA. In this study, we show that human topoisomerase I (topo I) and yeast topoisomerase II (topo II), each of which relax both positive and negative superhelical tension, reverse the transcriptional repression by chromatin. In the presence of bacterial topo I, which can relax only negative superhelical tension, the transcription is repressed on chromatin templates. The data together show that the relaxation of positive superhelical tension by these enzymes was the key property required for RNA synthesis from chromatin templates. In the absence of topoisomerase, transcriptional repression on chromatin depended on RNA length. The synthesis of transcripts of 100 nt or shorter was unaffected by chromatin, but repression was apparent when the RNA transcript was 200 nt or longer. These findings suggest that transcription on chromatin templates results in the accumulation of positive superhelical tension by the elongating polymerase, which in turn inhibits further elongation in the absence of topoisomerase activity.
Mondal
Neelima
N
Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
Zhang
Ye
Y
Jonsson
Zophonias
Z
Dhar
Suman Kumar
SK
Kannapiran
Madhu
M
Parvin
Jeffrey D
JD
D002166:Camptothecin / Q000494:pharmacology; D002843:Chromatin / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026942:DNA Topoisomerases / Q000378:metabolism*; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005047:Etoposide / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D009690:Nucleic Acid Conformation; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism; D012313:RNA / Q000235:genetics / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism*; D013698:Templates, Genetic; D059004:Topoisomerase I Inhibitors; D059003:Topoisomerase Inhibitors; D014158:Transcription, Genetic
D002843:Chromatin; D004791:Enzyme Inhibitors; D019384:Nucleic Acid Synthesis Inhibitors; D009707:Nucleosomes; D059004:Topoisomerase I Inhibitors; D059003:Topoisomerase Inhibitors; D012313:RNA; D005047:Etoposide; D004247:DNA; D012319:RNA Polymerase II; D026942:DNA Topoisomerases; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II; D002166:Camptothecin