title: Association of DNA topoisomerase I and RNA polymerase I: a possible role for topoisomerase I in ribosomal gene transcription.
abstract: RNA polymerase I preparations purified from a rat hepatoma contained DNA topoisomerase activity. The DNA topoisomerase associated with the polymerase had an Mr of 110,000, required Mg2+ but not ATP, and was recognized by anti-topoisomerase I antibodies. When added to RNA polymerase I preparations containing topoisomerase activity, anti-topoisomerase I antibodies were able to inhibit the DNA relaxing activity of the preparation as well as RNA synthesis in vitro. RNA polymerase II prepared by analogous procedures did not contain topoisomerase activity and was not recognized by the antibodies. The topoisomerase I: polymerase I complex was reversibly dissociated by column chromatography on Sephacryl S200 in the presence of 0.25 M (NH4)2SO4. Topoisomerase I was immunolocalized in the transcriptionally active ribosomal gene complex containing RNA polymerase I in situ. These data indicate that topoisomerase I and RNA polymerase I are tightly complexed both in vivo and in vitro, and suggest a role for DNA topoisomerase I in the transcription of ribosomal genes.
authors.affiliation: Department of Pharmacology, Medical School, University of Texas Health Science Center, Houston 77225.
authors.forename: K M
authors.initials: KM
authors.lastname: Rose
authors.forename: J
authors.initials: J
authors.lastname: Szopa
authors.forename: F S
authors.initials: FS
authors.lastname: Han
authors.forename: Y C
authors.initials: YC
authors.lastname: Cheng
authors.forename: A
authors.initials: A
authors.lastname: Richter
authors.forename: U
authors.initials: U
authors.lastname: Scheer
mesh_terms: D000818:Animals; D000906:Antibodies; D000936:Antigen-Antibody Complex; D004264:DNA Topoisomerases, Type I / Q000302:isolation & purification / Q000378:metabolism*; D004275:DNA, Ribosomal / Q000235:genetics*; D005455:Fluorescent Antibody Technique; D005796:Genes; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000201:enzymology*; D008970:Molecular Weight; D012318:RNA Polymerase I / Q000302:isolation & purification / Q000378:metabolism*; D051381:Rats; D014158:Transcription, Genetic
chemical_list: D000906:Antibodies; D000936:Antigen-Antibody Complex; D004275:DNA, Ribosomal; D012318:RNA Polymerase I; D004264:DNA Topoisomerases, Type I