Multiprotein complexes present at the MIF motifs flanking the promoter of the human c-myc gene

The activated C-myc allele in Burkitt's lymphoma is associated,vith a clust ering of somatic mutations within a discrete domain of intron I that define protein recognition sequences, designated as myc intron factors (MIF-1, MI F-2 and MIF-3). We have previously shown that MIF-1 binding activity consis ts of two polypeptides, myc intron binding polypeptide (MIBP1) and RFX1, In the present study we identified two polypeptides, p105 and p115, and showe d that these proteins give rise to a DNA-protein complex at the MIF-2 as we ll as the adjacent MIF-1 site. In addition, we demonstrated that all four p roteins interact with a navel MIF-I like motif upstream from the c-myc prom oter region, designated 5'MTF, These data suggest a model, where the intera ctions of MIBP1/RFX1 and p105/p115 with the MIF-like sites may play a role in the promoter topology of the c-myc gene. (C) 2000 Federation of European Biochemical Societies.