title: Diverged composition and regulation of the Trypanosoma brucei origin recognition complex that mediates DNA replication initiation.
abstract: Initiation of DNA replication depends upon recognition of genomic sites, termed origins, by AAA+ ATPases. In prokaryotes a single factor binds each origin, whereas in eukaryotes this role is played by a six-protein origin recognition complex (ORC). Why eukaryotes evolved a multisubunit initiator, and the roles of each component, remains unclear. In Trypanosoma brucei, an ancient unicellular eukaryote, only one ORC-related initiator, TbORC1/CDC6, has been identified by sequence homology. Here we show that three TbORC1/CDC6-interacting factors also act in T. brucei nuclear DNA replication and demonstrate that TbORC1/CDC6 interacts in a high molecular complex in which a diverged Orc4 homologue and one replicative helicase subunit can also be found. Analysing the subcellular localization of four TbORC1/CDC6-interacting factors during the cell cycle reveals that one factor, TbORC1B, is not a static constituent of ORC but displays S-phase restricted nuclear localization and expression, suggesting it positively regulates replication. This work shows that ORC architecture and regulation are diverged features of DNA replication initiation in T. brucei, providing new insight into this key stage of eukaryotic genome copying.
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Catarina A
authors.initials: CA
authors.lastname: Marques
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Calvin
authors.initials: C
authors.lastname: Tiengwe
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Leandro
authors.initials: L
authors.lastname: Lemgruber
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Jeziel D
authors.initials: JD
authors.lastname: Damasceno
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Scott
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Paape
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK.
authors.forename: Lucio
authors.initials: L
authors.lastname: Marcello
authors.affiliation: The Wellcome Trust Centre for Molecular Parasitology, Institute of Infection, Immunity and Inflammation, University of Glasgow, Sir Graeme Davis Building, 120 University Place, Glasgow, G12 8TA, UK richard.mcculloch@glasgow.ac.uk.
authors.forename: Richard
authors.initials: R
authors.lastname: McCulloch
mesh_terms: D002453:Cell Cycle; D002467:Cell Nucleus / Q000235:genetics; D004261:DNA Replication; D051738:Origin Recognition Complex / Q000378:metabolism* / Q000502:physiology; D015800:Protozoan Proteins / Q000378:metabolism* / Q000502:physiology; D014346:Trypanosoma brucei brucei / Q000235:genetics* / Q000378:metabolism
chemical_list: D051738:Origin Recognition Complex; D015800:Protozoan Proteins