ATP-Binding Cassette Properties of Recombination Mediator Protein RecF

1.1 Recombinational repair Homologous recombination (HR) is essential for genetic diversity and genome stability. The conserved RecA-like recombinases promote pairing and consequent exchange of fragments between two homologous DNA molecules during conjugation in bacteria and meiotic recombination in eukaryotes. HR is a main DNA repair pathway particularly important in case of large-scale DNA damages, including chromosome or double-stranded (ds) DNA breaks (DSBs) and long single-stranded (ss) DNA gaps (SSGs) (Cox, 1991; Kowalczykowski et al., 1994). The broken chain is paired with the intact DNA, which serves as a template for the synthesis of the damaged DNA. The same recombinases are also involved in the repair and origin-independent restart of stalled DNA replication, a frequently occurring event in every cell (Cox et al., 2000; Kowalczykowski, 2000; Kuzminov, 2001). HR is initiated by the cooperative binding of RecA recombinase to ssDNA hundreds or thousands nucleotides long forming nucleoprotein filament, a so called presynaptic complex often designated as RecA*. The presynaptic complex can bind homologous dsDNA and exchange a DNA strands. RecA* has multiple activities beyond the strand invasion and exchange (Figure 1). Those include triggering DNA damage SOS response through stimulation of LexA autocleavage (Rehrauer et al., 1996) and activation of UmuD subunit of the error-prone DNA polymerase PolV important for translesion synthesis to bypass small-scale DNA errors (Jiang et al., 2009; Rajagopalan et al., 1992). RecA* was also suggested to stabilize and maintain stalled replication fork during DNA repair (Courcelle et al., 1997). Consequently, RecA binding to DNA is regulated at multiple levels (Cox, 2007).