Characterization of a triple DNA polymerase replisome.
The replicase of all cells is thought to utilize two DNA polymerases for coordinated synthesis of leading and lagging strands. The DNA polymerases are held to DNA by circular sliding clamps. We demonstrate here that the E. coli DNA polymerase III holoenzyme assembles into a particle that contains three DNA polymerases. The three polymerases appear capable of simultaneous activity. Furthermore, the trimeric replicase is fully functional at a replication fork with helicase, primase, and sliding clamps; it produces slightly shorter Okazaki fragments than replisomes containing two DNA polymerases. We propose that two polymerases can function on the lagging strand and that the third DNA polymerase can act as a reserve enzyme to overcome certain types of obstacles to the replication fork.
McInerney
Peter
P
Laboratory of DNA Replication, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021, USA.
Johnson
Aaron
A
Katz
Francine
F
O'Donnell
Mike
M
D004258:DNA Polymerase III / Q000378:metabolism*; D004261:DNA Replication; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000378:metabolism*; D004789:Enzyme Activation; D004926:Escherichia coli / Q000201:enzymology*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D000099272:Replisomes
D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase; D009097:Multienzyme Complexes; D021122:Protein Subunits; D000099272:Replisomes; C023140:DNA replicase