title: Mechanism of the E. coli tau processivity switch during lagging-strand synthesis.
abstract: The E. coli replication machinery employs a beta clamp that tethers the polymerase to DNA, thus ensuring high processivity. The replicase also contains a processivity switch that dissociates the polymerase from its beta clamp. The switch requires the tau subunit of the clamp loader and is regulated by different DNA structures. At a primed site, the switch is "off." When the replicase reaches the downstream primer to form a nick, the switch is flipped, and tau ejects the polymerase from beta. This switch has high fidelity for completed synthesis, remaining "off" until just prior to incorporation of the last nucleotide and turning "on" only after addition of the last dNTP. These actions of tau are confined to its C-terminal region, which is located outside the clamp loading apparatus. Thus, this highly processive replication machine has evolved a mechanism to specifically counteract processivity at a defined time in the lagging-strand cycle.
authors.affiliation: Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
authors.forename: Frank P
authors.initials: FP
authors.lastname: Leu
authors.forename: Roxana
authors.initials: R
authors.lastname: Georgescu
authors.forename: Mike
authors.initials: M
authors.lastname: O'Donnell
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D004258:DNA Polymerase III / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D020035:Holoenzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D007700:Kinetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D021122:Protein Subunits; D014157:Transcription Factors
chemical_list: D004269:DNA, Bacterial; D020035:Holoenzymes; D021122:Protein Subunits; D014157:Transcription Factors; C041273:transcription factor tau; D004258:DNA Polymerase III