FRTlike

FRTlike refers to DNA sequences that resemble the canonical Flp recombination target (FRT) site and can be recognized by Flp recombinase. These FRTlike sequences may occur naturally in genomes or be engineered in experimental constructs to expand the repertoire of site-specific recombination options beyond the exact FRT site. They are characterized by partial similarity to the FRT motif and can mediate recombination events under appropriate conditions, though often with varying efficiency.

In terms of structure and mechanism, true FRT sites are 34 base pairs long and feature inverted repeats flanking a central spacer region. FRTlike sites retain some of these features but diverge from the consensus, which can affect whether Flp recombinase binds and catalyzes excision, inversion, or integration. The recombination outcome depends on sequence similarity, orientation of the sites, and the surrounding DNA context, as well as the specific Flp variant used.

Applications of FRTlike sequences include genome engineering strategies that require conditional or multi-step modifications. They are employed to introduce, delete, or rearrange genetic elements in systems where Cre-loxP or other recombination tools are already in use, providing additional flexibility. Researchers may identify FRTlike sites computationally or validate them experimentally to minimize off-target recombination and to tailor recombination efficiency.

Limitations and considerations include the risk of unintended recombination at FRTlike sites, dependence on chromatin state and methylation, and potential cross-reactivity with other recombinases. Engineered Flp variants with altered specificity can mitigate these challenges and enable more precise genome editing.

See also: Flp recombinase, FRT site, Cre-loxP system, site-specific recombination.