The mR3-3 mutant is defective in activating the mim-1 endogenous target gene and cannot be rescued by the VP16 activation domain. PCR was performed on ten fold serial dilutions of cDNA with primers specific for the mim-1 (676 bp) and β-actin (823 bp) genes. For mim-1 1:10^1;, 1:10^2;, and 1:10^3; dilutions are shown. For β-actin 1:10^2;, 1:10^3;, 1:10^4;, 1:10^5;, and 1:10^6; dilutions are shown. Expression of β-actin reveals that a similar amount of total RNA was used for each sample. Expression of mim-1 at a 1:10^3; dilution was detected for the full length wild-type c-Myb but no expression at any dilution was found for mR3-3. Complete absence of target gene activation was found for the mR3-3 DBD fused to VP16, while the wild-type c-MybVP did induce mim-1 expression. The 1 Kb Plus DNA molecular weight marker (Invitrogen) flanks each of the mim-1 samples and is at the left side of the β-actin gel. Sizes are 12,000 to 3000 bp for the top cluster of bands, then 2000 (arrows), 1650, 1000, 850, 650, and 500 bp for the lower bands.