FIGURE 1.

Binding of MBD_MBD4 to ^5mCG/^5mCG and ^5mCG/TG. A and B, representative autoradiographic images of competition assays for MBD_MBD4 (A) and MBD_MBD1 (B). Each competitor sequence is indicated above the lanes. The left panel in each section shows a control binding experiment in the absence of competitor DNA. C and D, each band was quantified relative to the total input DNA from the gel band density. The relative values were normalized against the control lane, and plotted against the amounts of competitor DNA. Each data point represents an average of three independent experiments using MBD_MBD4 (C) or MBD_MBD1 (D). Each solid line shows a curve fitted using Morrison's equation. An ∼1.5-fold excess of the nonlabeled ^5mCG/^5mCG fragment was required to obtain the same competitive effect as with nonlabeled ^5mCG/TG, indicating that MBD_MBD4 has a similar affinity for ^5mCG/TG and ^5mCG/^5mCG sites.