Regulation of Cre recombinase activity by mutated estrogen receptor ligand-binding domains

Ligand-dependent chimeric Cre recombinases are powerful tools to induce specific DNA rearrangements in cultured cells and in mice. We report here the construction and characterization of a series of chimeric recombinases, each consisting of Cre fused to a mutated human oestrogen receptor (ER) ligand-binding domain (LBD). Two new ligand-dependent recombinases which contain either the G400V/M543A/L544A or the G400V/L539A/L540A triple mutation of the human ER LBD are efficiently induced by the synthetic ER antagonists 4-hydroxytamoxifen (OHT) and ICI 182,780 (ICI), respectively, but are insensitive to 17 beta-oestradiol (E2). Both chimeric recombinases should be useful for efficient spatio-temporally controlled site-directed somatic mutagenesis.