FIG. 7.

Cdk1 and Cks1 bind directly to the histone H4 amino-terminal tail. (A) FLAG-tagged yeast Cdk1 (Cdc28) expressed and purified from E. coli was incubated with peptides corresponding to the biotinylated histone H3 and histone H4 amino-terminal tails bound to streptavidin beads or with unbound streptavidin beads. Eluates subjected to SDS-PAGE and blotting were assayed for FLAG-Cdk1 using anti-FLAG antibody and for biotinylated peptide using streptavidin-HRP. Lane −, no input and no histone H3 or H4 added (negative control). (B) Cks1 purified from E. coli was incubated and analyzed as described above for panel A using anti-Cks1 antibodies.