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  • 标题:Extensive purification of a putative RNA polymerase I holoenzyme from plants that accurately initiates rRNA gene transcription in vitro
  • 本地全文:下载
  • 作者:Julio Saez-Vasquez ; Craig S. Pikaard
  • 期刊名称:Proceedings of the National Academy of Sciences
  • 印刷版ISSN:0027-8424
  • 电子版ISSN:1091-6490
  • 出版年度:1997
  • 卷号:94
  • 期号:22
  • 页码:11869-11874
  • DOI:10.1073/pnas.94.22.11869
  • 语种:English
  • 出版社:The National Academy of Sciences of the United States of America
  • 摘要:RNA polymerase I (pol I) is a nuclear enzyme whose function is to transcribe the duplicated genes encoding the precursor of the three largest ribosomal RNAs. We report a cell-free system from broccoli (Brassica oleracea) inflorescence that supports promoter-dependent RNA pol I transcription in vitro. The transcription system was purified extensively by DEAE-Sepharose, Biorex 70, Sephacryl S300, and Mono Q chromatography. Activities required for pre-rRNA transcription copurified with the polymerase on all four columns, suggesting their association as a complex. Purified fractions programmed transcription initiation from the in vivo start site and utilized the same core promoter sequences required in vivo. The complex was not dissociated in 800 mM KCl and had a molecular mass of nearly 2 MDa based on gel filtration chromatography. The most highly purified fractions contain {approx}30 polypeptides, two of which were identified immunologically as RNA polymerase subunits. These data suggest that the occurrence of a holoenzyme complex is probably not unique to the pol II system but may be a general feature of eukaryotic nuclear polymerases.
  • 关键词:nucleolus ; rDNA ; gene expression
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