Convenient plasmid for extrachromosomal DNA recombination in mouse cells.

We constructed a convenient plasmid for DNA recombination assay. The plasmid, pMR1, contains a double prokaryotic terminator to decrease the background and two unique restriction enzyme sites on both sides of the double terminator to allow for easy construction. The assay is capable of selecting the bacterial cells containing recombined plasmid DNA on a selective plate containing ampicillin and chloramphenicol. We adapted pMR1 for V(D)J recombination and homologous recombination and detected both types of recombination in murine PreB cell line. As pMR1 has the double terminator, background on the selective plate decreases effectively and we select only the recombined clones. We consider the vector, pMR1, to be convenient for the analysis of homologous and non-homologous recombinations.