Max and c-Myc/Max DNA-binding activities in cell extracts

We have examined the interactions and DNA-binding activities of the c-Myc oncoprotein and its partner Max. In cell extracts virtually all c-Myc molecules are associated with Max in heterodimeric complexes. Moreover, DNA-binding studies with in vitro-translated protein and cell extracts show that both Max alone and c-Myc/Max bind the same DNA sequence. Conversely, c-Myc is unable to bind this sequence in the absence of Max. These findings suggest that c-Myc may function via obligate complex formation with Max.