A CDK interaction domain in c-Myb. (A) Deletion constructs. C-terminal deletion constructs of c-Myb were prepared using various restriction sites. The amino acid residues retained in each construct are shown at the right. The highly conserved DNA-binding domain of c-Myb is shaded black. (B) Mapping the interaction domains. The deletion constructs CP (lanes 1, 4), CH (lanes 2, 5), or CT (lanes 3, 6) were coexpressed with FLAG epitope-tagged CDK6 and the resulting complexes were isolated by immunoprecipitation with anti-FLAG beads then analyzed by Western blotting using anti-Myb antibodies, as described for Figure 1. The left panel (lanes 1-3) shows the total extracts; the immunoprecipitated samples are shown at the right (lanes 4-6). Arrows indicate the migration of the c-Myb protein derivatives. (C) Conservation of the CDK interaction domain. The amino acid sequences of v-Myb from avian myeloblastosis virus or c-Myb proteins from chicken, human, or mouse were aligned using ClustalW.⁴³  The bottom line shows the identical amino acids, shaded boxes show blocks of highest conservation. The numbering scheme comes from the chicken c-Myb protein.⁴⁴  The coiled-coil region predicted using the SMART analysis package^45,46  is indicated at bottom. The coiled-coil region has been shown to interact with the transcriptional coactivator CBP.⁴⁸