The ABC-primosome. A novel priming system employing dnaA, dnaB, dnaC, and primase on a hairpin containing a dnaA box sequence.
A priming mechanism requiring dnaA, dnaB, and dnaC proteins operates on a single-stranded DNA coated with single-stranded DNA-binding protein. This novel priming, referred to as "ABC-priming," requires a specific hairpin structure whose stem carries a dnaA protein recognition sequence (dnaA box). In conjunction with primase and DNA polymerase III holoenzyme, ABC-priming can efficiently convert single-stranded DNA into the duplex replicative form. dnaA protein specifically recognizes and binds the single-stranded hairpin and permits the loading of dnaB protein to form a prepriming protein complex containing dnaA and dnaB proteins which can be physically isolated. ABC-priming can replace phi X174 type priming on the lagging strand template of pBR322 in vitro, suggesting a possible function of ABC-priming for the lagging strand synthesis and duplex unwinding. Similar to the phi X174 type priming, a mobile nature of ABC-priming was indicated by helicase activity in the presence of ATP of a prepriming protein complex formed at the hairpin. The implications of this novel priming in initiation of replication at the chromosomal origin, oriC, and in its contribution to the replication fork are discussed.
Masai
H
H
Department of Molecular Biology, DNAX Research Institute of Molecular and Cellular Biology, Palo Alto, California 94304.
Nomura
N
N
Arai
K
K
D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism*; D010584:Bacteriophage phi X 174 / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002850:Chromatography, Gel; D004258:DNA Polymerase III / Q000378:metabolism; D019915:DNA Primase; D004261:DNA Replication; D004271:DNA, Fungal / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D015345:Oligonucleotide Probes; D010957:Plasmids; D012316:RNA Nucleotidyltransferases / Q000378:metabolism*
D001426:Bacterial Proteins; D004271:DNA, Fungal; D015345:Oligonucleotide Probes; D019915:DNA Primase; D012316:RNA Nucleotidyltransferases; D004258:DNA Polymerase III