title: Three-dimensional topology of the SMC2/SMC4 subcomplex from chicken condensin I revealed by cross-linking and molecular modelling.
abstract: SMC proteins are essential components of three protein complexes that are important for chromosome structure and function. The cohesin complex holds replicated sister chromatids together, whereas the condensin complex has an essential role in mitotic chromosome architecture. Both are involved in interphase genome organization. SMC-containing complexes are large (more than 650 kDa for condensin) and contain long anti-parallel coiled-coils. They are thus difficult subjects for conventional crystallographic and electron cryomicroscopic studies. Here, we have used amino acid-selective cross-linking and mass spectrometry combined with structure prediction to develop a full-length molecular draft three-dimensional structure of the SMC2/SMC4 dimeric backbone of chicken condensin. We assembled homology-based molecular models of the globular heads and hinges with the lengthy coiled-coils modelled in fragments, using numerous high-confidence cross-links and accounting for potential irregularities. Our experiments reveal that isolated condensin complexes can exist with their coiled-coil segments closely apposed to one another along their lengths and define the relative spatial alignment of the two anti-parallel coils. The centres of the coiled-coils can also approach one another closely in situ in mitotic chromosomes. In addition to revealing structural information, our cross-linking data suggest that both H2A and H4 may have roles in condensin interactions with chromatin.
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JR, UK.
authors.forename: Helena
authors.initials: H
authors.lastname: Barysz
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JR, UK Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia Department of Paediatrics, University of Melbourne, Parkville, Victoria 3052, Australia.
authors.forename: Ji Hun
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JR, UK.
authors.forename: Zhuo Angel
authors.initials: ZA
authors.lastname: Chen
authors.affiliation: Murdoch Children's Research Institute, Royal Children's Hospital, Parkville, Victoria 3052, Australia Department of Paediatrics, University of Melbourne, Parkville, Victoria 3052, Australia.
authors.forename: Damien F
authors.initials: DF
authors.lastname: Hudson
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JR, UK Department of Bioanalytics, Institute of Biotechnology, Technische Universität Berlin, 13355 Berlin, Germany juri.rappsilber@ed.ac.uk.
authors.forename: Juri
authors.initials: J
authors.lastname: Rappsilber
authors.affiliation: Foundation for Applied Molecular Evolution, PO Box 13174, Gainesville, FL 32604, USA dgerloff@ffame.org.
authors.forename: Dietlind L
authors.initials: DL
authors.lastname: Gerloff
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell Biology, University of Edinburgh, Michael Swann Building, Kings Buildings, Mayfield Road, Edinburgh EH9 3JR, UK bill.earnshaw@ed.ac.uk.
authors.forename: William C
authors.initials: WC
authors.lastname: Earnshaw
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry*; D000818:Animals; D002460:Cell Line; D002645:Chickens; D002875:Chromosomes; D004268:DNA-Binding Proteins / Q000737:chemistry*; D008040:Genetic Linkage; D006657:Histones / Q000378:metabolism; D008938:Mitosis; D008958:Models, Molecular; D046912:Multiprotein Complexes / Q000737:chemistry*; D009687:Nuclear Proteins / Q000737:chemistry*; D011487:Protein Conformation; D054730:Protein Interaction Domains and Motifs; D011993:Recombinant Fusion Proteins
chemical_list: D004268:DNA-Binding Proteins; D006657:Histones; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; C108312:condensin complexes; D000251:Adenosine Triphosphatases
keywords: SMC; coiled-coil; condensin; cross-linking; mass spectrometry; structure