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Reconstitution of plasmid DNA segregation from purified components
Author(s) -
Mullins R. Dyche,
Garner Ethan C,
Campbell Christopher S
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a208-c
Subject(s) - plasmid , biology , dna , chromosome segregation , genetics , homologous recombination , actin , protein filament , microbiology and biotechnology , gene , biophysics , chromosome
To ensure fidelity of gene transmission from mother cells to daughters, copies of a DNA molecule must be distributed among daughters before division. Several polymer‐based systems have evolved to accomplish this task. Eukaryotes harness the polymerization dynamics of tubulin to drive alignment and segregation of chromosomes during mitosis and in some eubacteria chromosome segregation requires assembly of actin‐like filaments. Extra‐chromosomal DNA elements must also ensure their inheritance by host progeny and many large, low‐copy plasmids have evolved their own polymer‐based DNA segregation machinery. To better understand polymer‐driven DNA segregation we reconstituted the segregation mechanism of the R1 drug‐resistance plasmid from purified components. R1 segregation is driven by the par operon, which is composed of three elements, parC, parR, and parM. The parR sequence encodes a protein that binds to the parC locus; and parM encodes an actin‐like protein that assembles into dynamically unstable filaments. The ParR/parC complex constructs a bipolar spindle by binding the ends of ParM filaments; inhibiting dynamic instability; and acting as a ratchet that permits incorporation of new monomers as it surfs on the growing filament ends. Under steady‐state conditions the dynamic instability of the unattached ParM filaments provides the energy to drive segregation.