Figure 7.
Schematic of the interactions of BUB1 and BUBR1 paralogs. A, elution profiles and SDS-PAGE analysis of SEC experiments with BUB1/BUB3, BUBR1/BUB3, eGFP-CENP-E2070-C, and mCherry-CENP-F2688-C, each at 6 μm loading concentration. The elution of eGFP-CENP-E2070-C and mCherry-CENP-F2688-C was additionally monitored through their fluorescence. B, schematic summarizes the interactions occurring at kinetochores between CENP-E, CENP-F, BUB1, and BUBR1. BUB1 is recruited to the kinetochore subunit Knl1 (see Introduction) after phosphorylation by the SAC kinase Mps1. There, BUB1 recruits BUBR1 through a pseudo-dimeric interaction (64). CENP-F kinetochore localization strictly depends on BUB1, whereas CENP-E recruitment requires a wider and still uncharacterized network of interactions, indicated by a question mark. RZZ and MAD1 recruitment, as well as the corona expansion, appear to be independent from CENP-E and CENP-F, and are not shown. An interaction of CENP-E and CENP-F has also been identified (gray arrow), but is not sufficient for CENP-F localization in absence of BUB1.