Involvement of the inverted repeat of the yeast 2-micron plasmid in Flp site-specific and RAD52-dependent homologous recombination

Site-specific recombination within the Saccharomyces cerevisiae 2-micron DN A plasmid is catalyzed by the Flp recombinase at specific Flp Recognition T arget (FRT) sites, which lie near the center of two precise 599-bp Inverted Repeats (IRs). However, the role of IR DNA sequences other than the. FRT i tself for the function of the Flp reaction in vivo is not known. In the pre sent work we report that recombination efficiency differs depending on whet her the FRT or the entire IR serves as the substrate for Flp. We also provi de evidence for the involvement of the IR in RAD52-dependent homologous rec ombination. In contrast, the catalysis of site-specific recombination betwe en two FRTs does not require the function of RAD52. The efficiency of Flp s ite-specific recombination between two IRs cloned in the same orientation i s about one hundred. times higher than that obtained when only the two FRTs are present. Moreover, we demonstrate that a single IR can activate RAD52- dependent homologous recombination between two flanking DNA regions, provid ing new insights into the role of the IR as a substrate for recombination a nd a new experimental tool with which to study the molecular mechanism of h omologous recombination.