title: A novel assay for examining the molecular reactions at the eukaryotic replication fork: activities of replication protein A required during elongation.
abstract: Studies to elucidate the reactions that occur at the eukaryotic replication fork have been limited by the model systems available. We have established a method for isolating and characterizing Simian Virus 40 (SV40) replication complexes. SV40 rolling circle complexes are isolated using paramagnetic beads and then incubated under replication conditions to obtain continued elongation. In rolling circle replication, the normal mechanism for termination of SV40 replication does not occur and the elongation phase of replication is prolonged. Thus, using this assay system, elongation phase reactions can be examined in the absence of initiation or termination. We show that the protein requirements for elongation of SV40 rolling circles are equivalent to complete SV40 replication reactions. The DNA produced by SV40 rolling circles is double-stranded, unmethylated and with a much longer length than the template DNA. These properties are similar to those of physiological replication forks. We show that proteins associated with the isolated rolling circles, including SV40 T antigen, DNA polymerase alpha, replication protein A (RPA) and RF-C, are necessary for continued DNA synthesis. PCNA is also required but is not associated with the isolated complexes. We present evidence suggesting that synthesis of the leading and lagging strands are co-ordinated in SV40 rolling circle replication. We have used this system to show that both RPA-protein and RPA-DNA interactions are important for RPA's function in elongation.
authors.affiliation: Department of Biochemistry, University of Iowa College of Medicine, 51 Newton Road, Iowa City, IA 52242-1109, USA.
authors.forename: A P
authors.initials: AP
authors.lastname: Walther
authors.forename: M P
authors.initials: MP
authors.lastname: Bjerke
authors.forename: M S
authors.initials: MS
authors.lastname: Wold
mesh_terms: D000957:Antigens, Viral, Tumor / Q000302:isolation & purification; D004265:DNA Helicases; D004256:DNA Polymerase I / Q000302:isolation & purification; D004261:DNA Replication; D004270:DNA, Circular; D004279:DNA, Viral / Q000096:biosynthesis*; D004268:DNA-Binding Proteins / Q000302:isolation & purification; D003852:Deoxyribonucleoproteins / Q000302:isolation & purification*; D005057:Eukaryotic Cells; D006367:HeLa Cells; D018398:Homeodomain Proteins; D006801:Humans; D018189:Immunomagnetic Separation; D046911:Macromolecular Substances; D015778:Minor Histocompatibility Antigens; D009690:Nucleic Acid Conformation; D011485:Protein Binding; D011506:Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D051818:Replication Protein C; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D013539:Simian virus 40 / Q000235:genetics*; D013997:Time Factors; D015534:Trans-Activators; D014779:Virus Replication
chemical_list: D000957:Antigens, Viral, Tumor; C096816:BCL2-related protein A1; D004270:DNA, Circular; D004279:DNA, Viral; D004268:DNA-Binding Proteins; D003852:Deoxyribonucleoproteins; D018398:Homeodomain Proteins; C096063:MATA1 protein, S cerevisiae; D046911:Macromolecular Substances; D015778:Minor Histocompatibility Antigens; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D015534:Trans-Activators; C045264:replication initiator protein; D004256:DNA Polymerase I; D004265:DNA Helicases; D051818:Replication Protein C