Fig. 1.

Mutants of Drosophila Myb. (A) (Top) Cartoon of the WT protein. The cyan boxes indicate the three conserved Myb repeats that constitute the paneukaryotic N-terminal DNA-binding domain. The red box indicates the conserved animal-specific C-terminal domain. The lines below the cartoon indicate the location of 17 previously undescribed alanine substitution mutants. Also shown are cartoons of the N-terminal (Middle; N-term) mutant (residues 1–316) and C-terminal (Bottom; C-term) mutant (residues 247–657). (B) Alignment of a conserved animal-specific C-terminal region that includes a previously described heat-sensitive hypomorphic Myb¹ mutant was made using MACAW software (NCBI) (34, 51). The three Myb genes of vertebrates arose via duplications that occurred before the divergence of all species examined thus far and are represented here by human MYB/C-MYB, MYBL1/A-MYB, and MYBL2/B-MYB (11).