Using an in vivo phagemid system to identify non-compatible loxP sequences(vol 499, pg 147, 2001)

The site-specific recombination system of bacteriophage P1 is composed of t he Cre recombinase that recognizes a 34-bp loxP site. The CrelloxP system h as been extensively used to manipulate eukaryotic genomes for functional ge nomic investigations. The creation of additional heterologous loxP sequence s potentially expands the utility of this system, but only if these loxP se quences do not recombine with one another. We have developed a stringent in vivo assay to examine the degree of recombination between all combinations of each previously published heterologous loxP sequence. As expected, homo logous loxP sequences efficiently underwent Cre-mediated recombination. How ever, many of the heterologous loxP pairs were able to support recombinatio n with rates varying from 5 to 100%. Some of these loxP sequences have prev iously been reported to be noncompatible with one another. Our study also c onfirmed other heterologous loxP pairs that had previously been shown to be non-compatible, as well as defined additional combinations that could be u sed in designing new recombination vectors. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reser ved.