Role of Escherichia coli DNA polymerase I in conferring viability upon the dnaN159 mutant strain.
The Escherichia coli dnaN159 allele encodes a mutant form of the beta-sliding clamp (beta159) that is impaired for interaction with the replicative DNA polymerase (Pol), Pol III. In addition, strains bearing the dnaN159 allele require functional Pol I for viability. We have utilized a combination of genetic and biochemical approaches to characterize the role(s) played by Pol I in the dnaN159 strain. Our findings indicate that elevated levels of Pol I partially suppress the temperature-sensitive growth phenotype of the dnaN159 strain. In addition, we demonstrate that the beta clamp stimulates the processivity of Pol I in vitro and that beta159 is impaired for this activity. The reduced ability of beta159 to stimulate Pol I in vitro correlates with our finding that single-stranded DNA (ssDNA) gap repair is impaired in the dnaN159 strain. Taken together, these results suggest that (i) the beta clamp-Pol I interaction may be important for proper Pol I function in vivo and (ii) in the absence of Pol I, ssDNA gaps may persist in the dnaN159 strain, leading to lethality of the dnaN159 DeltapolA strain.
Maul
Robert W
RW
Department of Biochemistry, School of Medicine and Biomedical Sciences, University at Buffalo, State University of New York, 3435 Main Street, Buffalo, NY 14214, USA.
Sanders
Laurie H
LH
Lim
James B
JB
Benitez
Rosemary
R
Sutton
Mark D
MD
D004256:DNA Polymerase I / Q000235:genetics / Q000378:metabolism*; D004258:DNA Polymerase III / Q000235:genetics*; D004260:DNA Repair; D004261:DNA Replication / Q000235:genetics; D004277:DNA, Single-Stranded; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000528:radiation effects; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D050296:Microbial Viability / Q000235:genetics* / Q000528:radiation effects; D009154:Mutation; D017422:Sequence Analysis, DNA; D013696:Temperature; D014466:Ultraviolet Rays
D004277:DNA, Single-Stranded; D029968:Escherichia coli Proteins; C101139:beta subunit, DNA polymerase III; D004256:DNA Polymerase I; D004258:DNA Polymerase III; D004259:DNA-Directed DNA Polymerase