The genome of the cell comprises a second recombination site.
This recombination site can further be recombined with a second polynucleotide, thus inserting the latter into the genomic DNA.
The enzymes and methods of the invention are suitable for mediating specific recombinations between DNA sequences comprising specific recombination sites without being limited to strict palindromic symmetry within each recombination site.
The method involves introducing a site-specific recombinase and a targeting construct, containing a first recombination site and the polynucleotide sequence of interest, into the mammalian cell.
The genome of the cell contains a second recombination site and recombination between the first and second recombination sites is facilitated by the site-specific, uni-directional recombinase.
Disclosed are variants of Cre recombinase that have broadened specificity for the site of recombination.