Vol 47(2013) N 2 p. 181-191;
I.V. Bakhlanova1, A.V. Dudkina1,2, D.M. Baitin1,2*
Enzymatic Control of Homologous Recombination and Hyperrecombination in Escherichia coli1Konstantinov Petersburg Nuclear Physics Institute, Gatchina, 188300 Russia
2St-Petersburg State Polytechnic University St-Petersburg, St-Petersburg, 195251 Russia
Received - 2012-03-22; Accepted - 2012-09-20
The RecA protein is a central homologous recombination enzyme in the bacterial cell. Forming a right-handed filament on ssDNA, RecA provides for a homology search between two DNA molecules and homologous strand exchange. RecA protects the cell from ionizing radiation and UV light and is capable of completing recombination during normal cell growth. Several mutant and natural RecA forms have a higher recombination potential in vitro and in vivo as compared with the wild-type Escherichia coli RecA, causing hyperrecombination. Recombinational hyperactivity of RecA depends to a great extent on the filamentation dynamics and DNA transferase properties, which may depend not only on specific amino acid substitutions in RecA, but also by defects in cell enzymatic machinery, including RecO, RecR, RecF, RecX, DinI, SSB, and PsiB. The functions of these proteins are currently known at the molecular level, while their roles in hyper-recombination are still incompletely understood. An increase in recombination in vivo is not always advantageous for the cell and is therefore limited by various mechanisms. In addition to the limitations imposed by cell enzymatic machinery, genomic rearrangements aimed at inhibiting the expression of hyperactive RecA are fixed through cell generations via selection against hyperrecombination. The mechanisms regulating hyperactive RecA forms in several model systems are considered.
RecA, SOS response, filament, regulation, recombination