Projects

Using purified proteins, we've reconstituted the initial steps of double-strand break repair by recombination-directed DNA replication. These studies have demonstrated that PriA directs the pathway of replication utilized at recombination intermediates.

A purified plasmid DNA replication system was used to demonstrate that Holliday junctions form as a result of nascent strand regression at stalled replication forks. We also showed that regression is favored by positive supercoiling and suppressed by negative supercoiling.

Two independent pathways of replisome assembly at stalled replication forks have been reconstituted with purified proteins. Interestingly, these 2 systems respond in inverse fashion to the presence of gaps in the nascent leading strand at the stalled fork.

We have shown that ParC and ParE, the 2 subunits of the cellular decatenase topoisomerase IV, reside in different locations in the cell. ParC is associated with the replication factory and ParE is found in the DNA-free spaces. This spatial separation imposes a temporal regulation on when the 2 subunits associate, which is at the end of the cell cycle.

We've found that topoisomerase IV associates with the septal ring protein FtsK and that the C-terminal AAA domain of FtsK stimulates the decatenation activity of topo IV. We think that this interaction is important for concentrating topo IV in the center of the cell during partition and cytokinesis.

We've identified SetB, an integral membrane protein that affects chromosome dynamics and associates with MreB, the bacterial actin ancestor. MreB and SetB are found in intertwining helical patterns in the cell, suggesting that SetB may help mediate forces on the chromosome generated by the MreB filament.