title: The Rix1 (Ipi1p-2p-3p) complex is a critical determinant of DNA replication licensing independent of their roles in ribosome biogenesis.
abstract: Several replication-initiation proteins are assembled stepwise onto replicators to form pre-replicative complexes (pre-RCs) to license eukaryotic DNA replication. We performed a yeast functional proteomic screen and identified the Rix1 complex members (Ipi1p-Ipi2p/Rix1-Ipi3p) as pre-RC components and critical determinants of replication licensing and replication-initiation frequency. Ipi3p interacts with pre-RC proteins, binds chromatin predominantly at ARS sequences in a cell cycle-regulated and ORC- and Noc3p-dependent manner and is required for loading Cdc6p, Cdt1p and MCM onto chromatin to form pre-RC during the M-to-G₁ transition and for pre-RC maintenance in G₁ phase-independent of its role in ribosome biogenesis. Moreover, Ipi1p and Ipi2p, but not other ribosome biogenesis proteins Rea1p and Utp1p, are also required for pre-RC formation and maintenance, and Ipi1p, -2p and -3p are interdependent for their chromatin association and function in pre-RC formation. These results establish a new framework for the hierarchy of pre-RC proteins, where the Ipi1p-2p-3p complex provides a critical link between ORC-Noc3p and Cdc6p-Cdt1p-MCM in replication licensing.
authors.affiliation: Division of Life Science, Center for Cancer Research and State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Kowloon, Hong Kong, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Huo
authors.forename: Rentian
authors.initials: R
authors.lastname: Wu
authors.forename: Zhiling
authors.initials: Z
authors.lastname: Yu
authors.forename: Yuanliang
authors.initials: Y
authors.lastname: Zhai
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Yang
authors.forename: Tsz-choi
authors.initials: TC
authors.lastname: Chan
authors.forename: Jeffrey T F
authors.initials: JT
authors.lastname: Yeung
authors.forename: Junsuo
authors.initials: J
authors.lastname: Kan
authors.forename: Chun
authors.initials: C
authors.lastname: Liang
mesh_terms: D002453:Cell Cycle / Q000235:genetics / Q000502:physiology; D018797:Cell Cycle Proteins / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000378:metabolism; D016193:G1 Phase / Q000502:physiology; D026341:Minichromosome Maintenance 1 Protein / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D051738:Origin Recognition Complex / Q000235:genetics / Q000378:metabolism; D020543:Proteome; D018741:Replication Origin; D012270:Ribosomes / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
chemical_list: C066503:CDC6 protein, S cerevisiae; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D026341:Minichromosome Maintenance 1 Protein; C429648:NOC3 protein, S cerevisiae; D009687:Nuclear Proteins; D029543:Nucleocytoplasmic Transport Proteins; C497214:ORC1 protein, S cerevisiae; D051738:Origin Recognition Complex; D020543:Proteome; C496539:Rix1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; C499592:TAH11 protein, S cerevisiae; D015534:Trans-Activators; C045264:replication initiator protein; D004265:DNA Helicases