FlpFRT

FlpFRT refers to the Flp recombinase and its recognition target sites (FRT) used to perform site-specific DNA rearrangements. Originating from the yeast Saccharomyces cerevisiae, the system is employed as a precise genetic engineering tool across a range of organisms, including yeast, plants, and mammals. Flp recombinase catalyzes recombination between two FRT sites, enabling controlled rearrangements of the DNA sequence between them. In practical use, researchers insert FRT sites at defined loci and express Flp to induce the desired DNA modification, such as excision, inversion, or, less commonly, insertion.

An FRT site is a 34-base pair DNA sequence recognized by Flp. It contains two directed, palindromic halves with a central, asymmetrical core. The orientation of the FRT sites determines the outcome: sites in the same orientation typically cause excision or replacement of the intervening DNA, while sites in opposite orientation cause an inversion of that segment. After recombination, the FRT site remains as a single, residual sequence at the junction.

Applications of FlpFRT include generating markerless deletions by removing selectable markers, constructing complex multi-gene configurations, and enabling cassette exchange or controlled expression in various model systems. In animal models, combining FlpFRT with other recombination systems such as Cre-loxP permits sophisticated genetic designs, including sequential or tissue-specific modifications.

Variants of Flp, such as FlpO or mammalian-optimized forms like Flpe and Flpo, offer improved activity in certain cell types and species. Considerations for use include potential off-target recombination at FRT-like sites and the need for appropriate promoters or inducible systems to control Flp expression.

Overall, FlpFRT remains a foundational tool for precise, programmable genome engineering and conditional genetic studies.