Cre

By Jamshed Arslan, Pharm. D., PhD.

Cyclization recombination enzyme (Cre) is a member of the extensive family of recombinases and recognizes a 34 bp sequence motif from PI bacteriophage referred to as LoxP. The Cre enzyme works to cleanly excise an intervening DNA fragment that is flanked by two LoxP sites. The LoxP sites must be present in the same orientation. The excised segment is later degraded to leave only a single LoxP site copy in the starting target molecule.

Cre (Cyclization recombination enzyme) is a member of the large family of recombinases. Cre recognizes Lox site loxP, a 34 bp sequence motif from the PI bateriophage. If a DNA segment is flanked by two loxP sites in the same orientation, Cre neatly excises the segment (for later degradation) leaving a single remaining loxP site in the DNA molecule. The Cre/Lox system was first developed in the late 1980's to artificially manipulate gene expression and extensive reviews of the system exist (1).