title: Identification of toposome, a novel multisubunit complex containing topoisomerase IIalpha.
abstract: Topoisomerase IIalpha plays essential roles in chromosome segregation. However, it is not well understood how topoisomerase IIalpha exerts its function during mitosis. In this report, we find that topoisomerase IIalpha forms a multisubunit complex, named toposome, containing two ATPase/helicase proteins (RNA helicase A and RHII/Gu), one serine/threonine protein kinase (SRPK1), one HMG protein (SSRP1), and two pre-mRNA splicing factors (PRP8 and hnRNP C). Toposome separates entangled circular chromatin DNA about fourfold more efficiently than topoisomerase IIalpha. Interestingly, this decatenation reaction yields knotted circles, which are not seen in reactions provided with monomeric circular DNA. Our results also show that interaction among toposome-associated proteins is highest in G2/M phase but drastically diminishes in G1/S phase. These results suggest that toposome is a dynamic complex whose assembly or activation is subject to cell cycle regulation.
authors.affiliation: Department of Biochemistry and Molecular Biology, Graduate School of Biomedical Sciences, University of Medicine and Dentistry of New Jersey, Newark 07013, USA. leecg@umdnj.edu
authors.forename: Chee-Gun
authors.initials: CG
authors.lastname: Lee
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Hague
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Robert
authors.initials: R
authors.lastname: Donnelly
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm; D002352:Carrier Proteins / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology*; D002467:Cell Nucleus / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000302:isolation & purification / Q000378:metabolism*; D004270:DNA, Circular / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D006367:HeLa Cells; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D009097:Multienzyme Complexes; D009690:Nucleic Acid Conformation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D021122:Protein Subunits / Q000378:metabolism; D020365:RNA Helicases / Q000378:metabolism; D016601:RNA-Binding Proteins; D013379:Substrate Specificity; D035602:Transcriptional Elongation Factors / Q000378:metabolism
chemical_list: D000951:Antigens, Neoplasm; D002352:Carrier Proteins; D004270:DNA, Circular; D004268:DNA-Binding Proteins; D034482:Heterogeneous-Nuclear Ribonucleoprotein Group C; D006609:High Mobility Group Proteins; D009097:Multienzyme Complexes; C115374:PRPF8 protein, human; D021122:Protein Subunits; D016601:RNA-Binding Proteins; C073537:SSRP1 protein, human; D035602:Transcriptional Elongation Factors; C087728:SRPK1 protein, human; D017346:Protein Serine-Threonine Kinases; D020365:RNA Helicases; D004250:DNA Topoisomerases, Type II