FIG. 6.
The BUB1-5 mitotic delay requires a functional kinase domain. (A) Wild-type cells carrying the indicated construct were induced in galactose for 4 h. Protein extracts were then prepared and subjected to gel electrophoresis and immunoblotting with Bub1p antibody. As previously described (20), multiple forms of Bub1p were observed. These have been determined to be due to different phosphorylation states (3b). (B) Wild-type cells carrying the indicated construct were synchronized with α-factor, released into galactose-containing medium, and examined for mitotic cells as described for Fig. 2A. The K733R mutation inactivates kinase function. ▪, PGAL>BUB1 plasmid; •, PGAL>BUB1-5 plasmid; ▴, PGAL>bub1-K733R plasmid; ◊, PGAL>bub1-5, K733R plasmid.