These results suggest that the regulation of the initiation process at the origin might indeed be dependent on the growth rate and that these changes still remain to be characterized quantitatively before they can be included in a theoretical model.
Thus, while oriC3 is independent of individual and pairwise combinations of Orc1/Cdc6 proteins, WhiP is required for replication initiation at this origin.
At the heart of the pX1.0 construct is an archetypical IncX1 replicon which encodes the replication initiation protein π, initiator of plasmid replication through a Cairns type (Θ type) mechanism at three discrete origins of replication (α, ß and γ), along with the Bis protein, required for replication initiation at the ß-origin.
Our model predicts initiation of replication at the origins, A2 and A1, on both inverted repeats, displacing opposite strands at each origin (Step 1 of Figure 10A).
It is possible that the ori-B sequences act as accessory units in the strand displacement process, after replication initiation at the A2 and A1 origins.
When multiple origins are present in the cell, the DnaA molecules "ejected" from one origin after initiation of replication are used for the initiation at other origins.
Casting defects are at the origin of crack initiation for all samples tested.
ADP bound form of DnaA is inactive for replication initiation, forming an important level of regulation at the origin.
In the first step, during the G1 phase key replication initiation factors, including the origin recognition complex, the Cdc6 protein and the MCM proteins 2 7 are recruited into PRCs at future replication origins, establishing the competence of particular chromatin regions for initiation of DNA synthesis (Tye, 1999; Labib and Diffley, 2001; Lei and Tye, 2001; Yu et al, 2004b).
Our results strongly suggest that the downstream region functions as a DNA unwinding element during replication initiation, leading to the formation of a persistent RNA-DNA hybrid at the origin.
