The beta clamp targets DNA polymerase IV to DNA and strongly increases its processivity.
The recent discovery of a new family of ubiquitous DNA polymerases involved in translesion synthesis has shed new light onto the biochemical basis of mutagenesis. Among these polymerases, the dinB gene product (Pol IV) is involved in mutagenesis in Escherichia coli. We show here that the activity of native Pol IV is drastically modified upon interaction with the beta subunit, the processivity factor of DNA Pol III. In the absence of the beta subunit Pol IV is strictly distributive and no stable complex between Pol IV and DNA could be detected. In contrast, the beta clamp allows Pol IV to form a stable initiation complex (t 1/2 approximately 2.3 min), which leads to a dramatic increase in the processivity of PoI IV reaching an average of 300-400 nucleotides. In vivo, the beta processivity subunit may target DNA Pol IV to its substrate, generating synthesis tracks much longer than previously thought.
Wagner
J
J
UPR 9003 du Centre National de la Recherche Scientifique Cancérogenèse et Mutagenèse Moléculaire et Structurale, UPR conventionnée avec l'Université de Strasbourg, France.
Fujii
S
S
Gruz
P
P
Nohmi
T
T
Fuchs
R P
RP
D001426:Bacterial Proteins / Q000378:metabolism / Q000502:physiology*; D004247:DNA / Q000378:metabolism*; D004249:DNA Damage; D004270:DNA, Circular / Q000378:metabolism; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D007700:Kinetics; D016296:Mutagenesis; D011485:Protein Binding; D013997:Time Factors
D001426:Bacterial Proteins; D004270:DNA, Circular; C094399:DinB protein, E coli; D029968:Escherichia coli Proteins; D004247:DNA