title: RPA is an initiation factor for human chromosomal DNA replication.
abstract: The initiation of chromosomal DNA replication in human cell nuclei is not well understood because of its complexity. To allow investigation of this process on a molecular level, we have recently established a cell-free system that initiates chromosomal DNA replication in an origin-specific manner under cell cycle control in isolated human cell nuclei. We have now used fractionation and reconstitution experiments to functionally identify cellular factors present in a human cell extract that trigger initiation of chromosomal DNA replication in this system. Initial fractionation of a cytosolic extract indicates the presence of at least two independent and non-redundant initiation factors. We have purified one of these factors to homogeneity and identified it as the single-stranded DNA binding protein RPA. The prokaryotic single-stranded DNA binding protein SSB cannot substitute for RPA in the initiation of human chromosomal DNA replication. Antibodies specific for human RPA inhibit the initiation step of human chromosomal DNA replication in vitro. RPA is recruited to DNA replication foci and becomes phosphorylated concomitant with the initiation step in vitro. These data establish a direct functional role for RPA as an essential factor for the initiation of human chromosomal DNA replication.
authors.affiliation: Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
authors.forename: Dávid
authors.initials: D
authors.lastname: Szüts
authors.forename: Lisa
authors.initials: L
authors.lastname: Kitching
authors.forename: Christo
authors.initials: C
authors.lastname: Christov
authors.forename: Aidan
authors.initials: A
authors.lastname: Budd
authors.forename: Sew
authors.initials: S
authors.lastname: Peak-Chew
authors.forename: Torsten
authors.initials: T
authors.lastname: Krude
mesh_terms: D002460:Cell Line; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004261:DNA Replication; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D006367:HeLa Cells; D006801:Humans; D010766:Phosphorylation; D011485:Protein Binding; D051716:Replication Protein A
chemical_list: D004268:DNA-Binding Proteins; C497167:RPA1 protein, human; D051716:Replication Protein A; D004247:DNA