title: Human replication protein A binds single-stranded DNA in two distinct complexes.
abstract: Human replication protein A, a single-stranded DNA (ssDNA)-binding protein, is a required factor in eukaryotic DNA replication and DNA repair systems and has been suggested to function during DNA recombination. The protein is also a target of interaction for a variety of proteins that control replication, transcription, and cell growth. To understand the role of hRPA in these processes, we examined the binding of hRPA to defined ssDNA molecules. Employing gel shift assays that "titrated" the length of ssDNA, hRPA was found to form distinct multimeric complexes that could be detected by glutaraldehyde cross-linking. Within these complexes, monomers of hRPA utilized a minimum binding site size on ssDNA of 8 to 10 nucleotides (the hRPA8-10nt complex) and appeared to bind ssDNA cooperatively. Intriguingly, alteration of gel shift conditions revealed the formation of a second, distinctly different complex that bound ssDNA in roughly 30-nucleotide steps (the hRPA30nt complex), a complex similar to that described by Kim et al. (C. Kim, R. O. Snyder, and M. S. Wold, Mol. Cell. Biol. 12:3050-3059, 1992). Both the hRPA8-10nt and hRPA30nt complexes can coexist in solution. We speculate that the role of hRPA in DNA metabolism may be modulated through the ability of hRPA to bind ssDNA in these two modes.
authors.affiliation: Department of Biochemistry, New York University Medical Center, New York 10016.
authors.forename: L J
authors.initials: LJ
authors.lastname: Blackwell
authors.forename: J A
authors.initials: JA
authors.lastname: Borowiec
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D002455:Cell Division; D004260:DNA Repair; D004261:DNA Replication; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008961:Models, Structural; D008969:Molecular Sequence Data; D009838:Oligodeoxyribonucleotides / Q000138:chemical synthesis / Q000378:metabolism; D051716:Replication Protein A; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic
chemical_list: D004277:DNA, Single-Stranded; D004268:DNA-Binding Proteins; D009838:Oligodeoxyribonucleotides; C497167:RPA1 protein, human; D051716:Replication Protein A