Overexpression of bacterial RecA protein stimulates homologous recombination in somatic mammalian cells.

The pairing of homologous molecules and strand exchange is a key event in homologous recombination promoted by RecA protein in Escherichia coli. Structural homologs of RecA are widely distributed in eukaryotes including mouse and man. As has been shown, human HsRad51 protein is not only structural but also functional homolog of RecA. The question arises whether the bacterial functional homolog of Rad51 can function in mammalian cells and increase the frequency of the homologous recombination. To investigate possible effects of bacterial RecA protein on the frequency of homologous recombination in mammalian cells, the E. coli RecA protein fused with a nuclear location signal from the large T antigen of simian virus 40 was overexpressed in the mouse F9 teratocarcinoma cells. We found that the frequency of gene targeting at the hprt locus was 10-fold increased in the mouse cells expressing the nucleus-targeted RecA protein. Southern blot analysis of individual clones that were generated by targeting recombination revealed predicted type of alterations in hprt gene. The data indicate that the bacterial nucleus-targeted RecA protein can stimulate homologous recombination in mammalian cells.