log in  |  register  |  feedback?  |  help  |  web accessibility
Logo
Organizing the bacterial chromosome for division
Chase Broedersz - Princeton University
Monday, October 28, 2013, 4:00-5:00 pm Calendar
  • You are subscribed to this talk through .
  • You are watching this talk through .
  • You are subscribed to this talk. (unsubscribe, watch)
  • You are watching this talk. (unwatch, subscribe)
  • You are not subscribed to this talk. (watch, subscribe)
Abstract

The chromosomal segregation machinery in bacteria such as Caulobacter crescentus and Bacillus subtilis includes the ParABS partitioning system. This segregation machinery includes a large ParB-DNA complex, localized near the origin of replication on the chromosome, consisting of ~1000 ParB proteins clustered around one or a few centromeric parS sites. During segregation the ParB-DNA complex associates with a ParA spindle-like apparatus. Despite the apparent simplicity of  this  segregation machinery, puzzles remain: What is the nature of interactions among DNA-bound ParB proteins, and how do these determine the organizational and functional properties of the ParB-DNA partitioning complex? A crucial aspect of this question is whether ParB spreads along the DNA to form a filamentous complex with a one-dimensional character, or rather aggregates to form a three-dimensional complex on the DNA. Furthermore,  it remains unclear how the presence of only one or even a few centromeric parS sites can lead to robust formation and localization of a large protein-DNA complex. We developed a simple model for interacting proteins on DNA and found that a combination of 1D spreading bonds and a single 3D bridging bond between ParB proteins constitutes the minimal model for condensation of a three-dimensional ParB-DNA complex. These combined interactions provide an effective surface tension that prevents fragmentation of the ParB-DNA complex. Thus, conceptually, the partitioning complex is described as a 3D ParB-DNA condensate, which is formed through a phase transition.

 

 

This talk is organized by Star Jackson