A 0.9 kb DNA fragment containing the cytomegalovirus early gene promoter was fused to the rabbit beta-globin second intron and chloramphenicol acetyltransferase (CAT) gene cassette connected to a polyadenylation signal, both ends of which were flanked by loxP sites. This was then followed by a 0.6 kb DNA fragment encoding a dominant-negative mutant for RhoA and a second polyadenylation signal. (J:100207)