Expression of MEL1S in the t(1;3)(p36;q21)-positive leukemia cells. (A) Cell extracts from t(1;3)(p36;q21)-positive or -negative leukemia immunoprecipitated with anti-MELDBD1 antibody were separated by 6% SDS–polyacrylamide gel electrophoresis followed by immunoblotting with the anti-MELDBD1 antibody (IP-Blot). Also, extracts from COS7 cells with each CMV expression vector were used as controls for immunoblotting analysis (Blot). Lanes represent MOLT15 (lane 1); U937 (lane 2); K562 (lane 3); UCSD/AML1 (lane 4); the t(1;3)(p36;q21)-positive leukemia cells (lane 5); and COS7 cells with a mock vector (pCMV; lane 6), MEL1 (pCMV-MEL1; lane 7), or MEL1S (pCMV-MEL1S; lane 8); and Δ13MEL1 (pCMV-Δ13MEL1; lane 9). As an internal control for immunoblot, a 40-kDa band of β-actin was shown at the bottom (lanes 6-9). Molecular weight markers (lane 10) are given in kilodaltons. (B) SDS-PAGE of polypeptides derived from V8 protease digestion or CNBr cleavage of MEL1S, Δ13MEL1, and the 150-kDa band from t(1;3)-positive leukemia. The first 5 lanes are V8 protease–digested samples from COS7 cells transfected by a mock vector (lane 1), MEL1S (lane 2), or Δ13MEL1 (lane 3), the 150-kDa band from t(1;3)-positive leukemia cells (lane 4), and V8 protease alone (lane 5). The last 4 lanes are CNBr cleavage samples indicated at the top of each lane. Molecular weight markers (lanes 6 and 11) are given in kilodaltons.