Enhanced cell-permeant Cre protein for site-specific recombination in cultured cells.

Background: Cell-permeant Cre DNA site-specific recombinases provide an easily controlled means to regulate gene structure and function in living cells. Since recombination provides a stable and unambiguous record of protein uptake, the enzyme may also be used for quantitative studies of cis- and trans-acting factors that influence the delivery of proteins into cells.

Results: In the present study, 11 recombinant fusion proteins were analyzed to characterize sequences and conditions that affect protein uptake and/or activity and to develop more active cell-permeant enzymes.