Analysis of the DNA-binding activity of Myc, Mad1, and Max complexes during induced differentiation of U-937 cells. (A) Lysates from untreated U-937-myc-6, U-937-neo-6, and U-937-GTB cells or cells induced by TPA for 3 days were subjected to SODA.33The lysates were immunoprecipitated under low stringency conditions by using specific antisera and incubated with ³²P-labeled CMD oligonucleotide, containing a Myc/Mac binding site or a mutated version (CMM) after which the amount of bound oligonucleotide was measured. The specificity was determined by competition with an excess of cold CMD or CMM oligonucleotide and by using preimmune (PI) serum. (B) Kinetic study of the DNA binding of total Myc-, v-Myc-, and total Max-containing and Mad1-containing complexes during differentiation of U-937-myc-6 cells. The cells were induced with TPA, IFN-γ, or the TPA + IFN-γ for the indicated time and subjected to SODA as in (A). The antisera used in (A) and (B) were IG-13 (anti-pan-Myc), 5042 (anti-chicken Myc), 266-4 (anti-Mad1) or 91-4 (anti-Max). The results are presented as a percentage of untreated cells. The error bars represent the standard deviations of the means from at least three independent experiments.