The C-terminal portion of B-myb interacts with cyclin A1 in a GST precipitation assay.

Different portions of B-myb were fused in frame to GST (“Materials and methods”) and bound to glutathione beads. These were incubated with U937 lysates for 2 hours. SDS sample buffer was added to the extensively washed beads. Proteins were electrophoresed, blotted on nitrocellulose, and subjected to Western blotting with the indicated antibodies. Lysate (20 μL total) and cyclin A1 expressed in Sf9 insect cells (upper gel) were run in parallel. Overexposed films are shown for cyclin A2 and cdk2 to demonstrate that even prolonged exposure of the blots did not lead to the appearance of specific bands in any lane except for the lysate. The band in the aa 1-183 lane of the cdk2 Western blot runs slower than the band seen for cdk2.