Figure 2.

DNA substrates containing both 5′ and 3′ ss tails are essential for processive helicase activity of the Mcm4/6/7 complex. (A) Increasing levels of the Mcm4/6/7 complex were incubated with 10 fmol of helicase substrates containing a 40-nt 5′ oligo(dT) ss region and varying lengths of 3′ ss tail as indicated. □, Reactions carried out with a substrate containing no 3′ tail; ◊, substrate with a 30-nt 3′ tail; ▴, substrate containing a 40-nt 3′ tail; ○, substrate with a 50-nt 3′ tail; ●, substrate with a 60-nt 3′ tail. (B) Helicase assays were performed with 10 fmol of DNA containing a 3′ oligo(dT) ss region of 50 nt in length and varying lengths of oligo(dT) at the 5′ end as indicated. □, No 5′ tail; ■, 10-nt 5′ tail; ◊, 15-nt 5′ tail; ▴, 20-nt 5′ tail; ○, 30-nt 5′ tail; and ●, 40-nt 5′ tail.