Pim-1 interacts with RUNX family proteins. (A) Yeast strains expressing the VP16 activation domain alone or fused with the B19 fragment of human RUNX3 were mated with strains expressing the GAL4 DNA-binding domain fused with the control protein lamin or either kinase-deficient (K67M) or wild-type (WT) Pim-1. The ability of two proteins to interact with each other was judged based on the capacity ot the corresponding diploid strains to grow on the selective medium lacking histidine. (B) COS-7 cells were transfected with pSV-pim-1, pAMC-Runx1 or pAMC-Runx3 plasmids as indicated in the figure. Parts of the cell lysates were subjected to immunoprecipitation with anti-Myc antibody followed by immunoblotting with anti-Pim-1 or anti-Myc antibodies. The expression of proteins in the lysates was verified by direct Western blotting with the same antibodies.