In gel shift assays, MCM4/6/7 bound to all the three bubbles, although the affinity to Bub82/c-myc/DUE and to Bub82/c-myc/DUE-C is slightly lower than that to Bub-82/lamin B2 (Figure 7B). Therefore, helicase and DNA binding activities do not necessarily correlate with each other. This was also indicated by our previous results that guanine and cytosine stretches can bind to Mcm but cannot activate the helicase (13).