Infection efficiencies of retroviruses expressing AML1 or its mutants. (A) The efficiency of retrovirus-mediated gene transfer of AML1 or its mutants was estimated by infecting NIH3T3 cells. Retrovirus-infected cells were evaluated by the expression of GFP (shaded histograms). Also shown are the noninfected NIH3T3 cells (open histograms). All the retroviruses infected more than 80% of NIH3T3 cells. (B) Expression of AML1 or its mutant proteins in infected NIH3T3 cells. The expression is monitored by immunoblotting of whole-cell lysates with anti-AML1.