Organizing the bacterial chromosome for division

Organizing the bacterial chromosome for division
Chase Broedersz, Princeton University
Date and time: Thu, Mar 27, 2014 - 11:15am
Refreshments at 11:00am
Location: LGRT 1033
Category: Condensed Matter Seminar
Abstract:
The organization of the bacterial chromosome is complicated by the requirement for replication and segregation. Chromosome segregation is mediated by partitioning proteins of the ParABS system in a variety of bacteria. At its heart, this segregation machinery includes a large protein-DNA complex consisting of roughly 1000 ParB proteins. The nature of interactions between DNA-bound ParB proteins, and how these determine the structural properties of the partitioning module remain unclear. To uncover the biophysical principles that determine the organization of the partitioning complex, we developed a simple model for interacting proteins on DNA. We found that a combination of 1D spreading bonds and a 3D bridging bond between ParB proteins constitutes a minimal model for condensation of a 3D ParB-DNA complex. These combined interactions provide an effective surface tension that prevents fragmentation of the ParB-DNA complex. The central predictions of this model directly address recent experiments on ParB-induced gene-silencing and the effect of a DNA "roadblock" on ParB localization. Furthermore, our model provides a simple mechanism to explain how a single centromeric parS site on the DNA is both necessary and sufficient for the formation and localization of the ParB-DNA complex.