RECC

RecC is a subunit of the bacterial RecBCD enzyme complex, which initiates repair of double-strand breaks by processing DNA ends to generate single-stranded DNA for homologous recombination. RecC, along with RecB and RecD, forms the helicase-nuclease complex that binds to broken DNA ends and unwinds the duplex while degrading one strand.

RecC's primary role is recognition of specific DNA motifs known as Chi sites. In Escherichia coli, the Chi consensus is 5'-GCTGGTGG-3'. When RecBCD encounters a Chi site, RecC interacts with the complex to modulate nuclease activity, reducing degradation of the 3' strand and promoting the production of a 3' overhang suitable for RecA loading. This Chi-dependent switch increases the efficiency of homologous recombination.

RecC also provides a physical channel through which single-stranded DNA threads as RecB and RecD unwind the DNA. It interacts with RecB and RecD and is essential for directed processing of DNA ends toward recombination rather than continuous degradation.

Genetically, recC is part of the recBCD operon. Mutations in recC can impair Chi recognition and reduce recombination efficiency, affecting survival after DNA damage. RecC is widely conserved among bacteria that rely on RecBCD-mediated repair, with variations in Chi recognition across species.

In research, RecC serves as a model for studying DNA end processing and the regulation of recombination, as well as for understanding how cells balance DNA degradation with repair.