title: A Role of hIPI3 in DNA Replication Licensing in Human Cells.
abstract: The yeast Ipi3p is required for DNA replication and cell viability in Sacharomyces cerevisiae. It is an essential component of the Rix1 complex (Rix1p/Ipi2p-Ipi1p-Ipi3p) that is required for the processing of 35S pre-rRNA in pre-60S ribosomal particles and for the initiation of DNA replication. The human IPI3 homolog is WDR18 (WD repeat domain 18), which shares significant homology with yIpi3p. Here we report that knockdown of hIPI3 resulted in substantial defects in the chromatin association of the MCM complex, DNA replication, cell cycle progression and cell proliferation. Importantly, hIPI3 silencing did not result in a reduction of the protein level of hCDC6, hMCM7, or the ectopically expressed GFP protein, indicating that protein synthesis was not defective in the same time frame of the DNA replication and cell cycle defects. Furthermore, the mRNA and protein levels of hIPI3 fluctuate in the cell cycle, with the highest levels from M phase to early G1 phase, similar to other pre-replicative (pre-RC) proteins. Moreover, hIPI3 interacts with other replication-initiation proteins, co-localizes with hMCM7 in the nucleus, and is important for the nuclear localization of hMCM7. We also found that hIPI3 preferentially binds to the origins of DNA replication including those at the c-Myc, Lamin-B2 and β-Globin loci. These results indicate that hIPI3 is involved in human DNA replication licensing independent of its role in ribosome biogenesis.
authors.affiliation: Biomedical Research Institute, Shenzhen-PKU-HKUST Medical Center, Shenzhen, China.|Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.|HKUST Fok Ying Tung Research Institute, Guangzhou, China.
authors.forename: Yining
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Aftab
authors.initials: A
authors.lastname: Amin
authors.affiliation: Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Biomedical Research Institute, Shenzhen-PKU-HKUST Medical Center, Shenzhen, China.|Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.|HKUST Fok Ying Tung Research Institute, Guangzhou, China.
authors.forename: Ziyi
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Huadong
authors.initials: H
authors.lastname: Jiang
authors.affiliation: Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Lu
authors.initials: L
authors.lastname: Liang
authors.affiliation: Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.
authors.forename: Linjing
authors.initials: L
authors.lastname: Shi
authors.affiliation: Biomedical Research Institute, Shenzhen-PKU-HKUST Medical Center, Shenzhen, China.|Division of Life Science, Center for Cancer Research and State Key Lab for Molecular Neuroscience, Hong Kong University of Science and Technology, Hong Kong, China.|HKUST Fok Ying Tung Research Institute, Guangzhou, China.|Intelgen Ltd., Hong Kong-Guangzhou-Foshan, China.
authors.forename: Chun
authors.initials: C
authors.lastname: Liang
mesh_terms: D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002843:Chromatin / Q000235:genetics / Q000378:metabolism*; D047369:Chromatin Immunoprecipitation; D004261:DNA Replication; D005455:Fluorescent Antibody Technique; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D064168:Minichromosome Maintenance Complex Component 7 / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012270:Ribosomes / Q000235:genetics / Q000378:metabolism; D020798:Two-Hybrid System Techniques
chemical_list: C103706:CDC6 protein, human; D018797:Cell Cycle Proteins; D002843:Chromatin; D009687:Nuclear Proteins; D012333:RNA, Messenger; C558249:WDR18 protein, human; C101624:MCM7 protein, human; D064168:Minichromosome Maintenance Complex Component 7