An actin-based mechanism of DNA segregation in bacteria
Despite decades of investigation, the mechanisms of chromosome segregation in bacteria remain unclear. Bacterial plasmids had long been used as models for segregation and several genes required for plasmid segregation had been isolated and characterized. These genes appeared to be related to genes on the host chromosome that might also be involved in segregation of DNA.
The Gerdes group had worked on the segregation genes of the low copy number E. coli plasmid R1 for many years. It was known that efficient segregation of R1 required a DNA-binding protein ParR, a target site for ParR binding on the plasmid, parC, and a protein ParM of unknown function. In ground-breaking work they discovered that ParM polymerises to form actin-like filaments, to the ends of which are associated copies of the plasmid. In collaboration with Lowe’s group they showed that the structure of ParM is congruent with that of eukaryotic actin. This work reinforced the emerging idea that actin evolved in bacteria long before the appearance of eukaryotes and provided for the first time a biochemical mechanism for DNA segregation in bacteria.
Møller-Jensen J, Borch J, Dam M, Jensen RB, Roepstorff P and Gerdes K. 2003. Bacterial Mitosis: ParM R1 moves plasmid DNA by an actin-like insertional polymerization mechanism. Molecular Cell 12, 1477–1487.
van den Ent F, Møller-Jensen J, Amos LA, Gerdes K and Löwe J. 2002. F-actin-like filaments formed by plasmid segregation protein ParM. EMBO Journal 21, 6935-6943.
Møller-Jensen J, Jensen RB, Lowe J, and Gerdes K. 2002. Prokaryotic DNA segregation by an actin-like filament. EMBO Journal 21, 3119-3127.
