Ij. Fijalkowska et al., UNEQUAL FIDELITY OF LEADING-STRAND AND LAGGING-STRAND DNA-REPLICATIONON THE ESCHERICHIA-COLI CHROMOSOME, Proceedings of the National Academy of Sciences of the United Statesof America, 95(17), 1998, pp. 10020-10025
We have investigated the question whether during chromosomal DNA repli
cation in Escherichia coli the two DNA strands may be replicated with
differential accuracy. This possibility of differential replication fi
delity arises from the distinct modes of replication in the two strand
s, one strand (the leading strand) being synthesized continuously, the
other (the lagging strand) discontinuously in the form of short Okaza
ki fragments. We have constructed a series of lacZ strains in which th
e lac operon is inserted into the bacterial chromosome in the two poss
ible orientations with regard to the chromosomal replication origin or
iC. Measurement of lac reversion frequencies for the two orientations,
under conditions in which mutations reflect replication errors, revea
led distinct differences in mutability between the two orientations. A
s gene inversion causes a switching of leading and lagging strands, th
ese findings indicate that leading and lagging strand replication have
differential fidelity. Analysis of the possible mispairs underlying e
ach specific base pair substitution suggests that the lagging strand r
eplication on the E. coli chromosome may be more accurate than leading
strand replication.