The lysates were incubated with 10 μg of poly(dI-dC) (Sigma) and 70 μl of streptavidin-agarose (Amersham Biosciences) carrying biotinylated oligonucleotides, for 3 h at 4 °C. The beads were washed twice with buffer C:D (1:3) and resuspended in DTT-containing loading buffer (NuPAGE; Invitrogen), heated to 70 °C for 10 min, and the eluants on a NuPAGE 4–12% bis-tris gel (Invitrogen).