UNWINDING OF THE ESCHERICHIA-COLI ORIGIN OF REPLICATION (ORIC) CAN OCCUR IN THE ABSENCE OF INITIATION PROTEINS BUT IS STABILIZED BY DNAA AND HISTONE-LIKE PROTEINS IHF OR HU
P. Polaczek et al., UNWINDING OF THE ESCHERICHIA-COLI ORIGIN OF REPLICATION (ORIC) CAN OCCUR IN THE ABSENCE OF INITIATION PROTEINS BUT IS STABILIZED BY DNAA AND HISTONE-LIKE PROTEINS IHF OR HU, Plasmid, 39(1), 1998, pp. 77-83
The unwinding of the origin of replication (oriC) is a critical step i
n initiation of DNA replication in Escherichia coli. Previous observat
ions indicate that efficient unwinding of supercoiled plasmid template
s containing oriC sequences requires the DnaA initiation protein and o
ne or more accessory factors. The precise contribution of each protein
to this process is unknown. Here, we demonstrate that unwinding can o
ccur under physiological conditions at the same bases in oriC, in eith
er the presence or the absence of initiation proteins, as detected by
a single-strand specific nuclease, P1. This suggests that oriC unwindi
ng is a spontaneous event determined solely by DNA sequence. DnaA and
IHF, as part of a large nucleoprotein complex, may function to stabili
ze the DNA strand opening prior to initiation of DNA replication. (C)
1998 Academic Press.