Nuclear factors interacting with the MS7 probe and identification of nucleotides involved in recognition of CEBP-100. (A) EMSA was performed on the MS7 oligonucleotide using nuclear extracts from COS-7 cells transfected with expression vectors for the indicated transcription factors. (B) EMSA was performed on the MS7 oligonucleotide using nuclear extracts from COS-7 cells transfected with either C/EBPα42 or RUNX1 plus CBFβ and in the absence or in the presence of the indicated competitor oligonucleotides. In all cases, the position of RUNX1- and C/EBP-containing complexes is indicated.