The roles of Fzy/Cdc20 and Fzr/Cdh1 in regulating the destruction of cyclin B in space and time.

Journal article

In Drosophila cells cyclin B is normally degraded in two phases: (a) destruction of the spindle-associated cyclin B initiates at centrosomes and spreads to the spindle equator; and (b) any remaining cytoplasmic cyclin B is degraded slightly later in mitosis. We show that the APC/C regulators Fizzy (Fzy)/Cdc20 and Fzy-related (Fzr)/Cdh1 bind to microtubules in vitro and associate with spindles in vivo. Fzy/Cdc20 is concentrated at kinetochores and centrosomes early in mitosis, whereas Fzr/Cdh1 is concentrated at centrosomes throughout the cell cycle. In syncytial embryos, only Fzy/Cdc20 is present, and only the spindle-associated cyclin B is degraded at the end of mitosis. A destruction box-mutated form of cyclin B (cyclin B triple-point mutant [CBTPM]-GFP) that cannot be targeted for destruction by Fzy/Cdc20, is no longer degraded on spindles in syncytial embryos. However, CBTPM-GFP can be targeted for destruction by Fzr/Cdh1. In cellularized embryos, which normally express Fzr/Cdh1, CBTPM-GFP is degraded throughout the cell but with slowed kinetics. These findings suggest that Fzy/Cdc20 is responsible for catalyzing the first phase of cyclin B destruction that occurs on the mitotic spindle, whereas Fzr/Cdh1 is responsible for catalyzing the second phase of cyclin B destruction that occurs throughout the cell. These observations have important implications for the mechanisms of the spindle checkpoint.

Authors: Raff, J; Jeffers, K; Huang, J

• Publication status: Published
• Journal: Journal of cell biology
• Volume: 157
• Issue: 7
• Pages: 1139-1149
• Publication date: 2002-06-01
• DOI: 10.1083/jcb.200203035
• EISSN: 1540-8140
• ISSN: 0021-9525
• Language: English
• Keywords: Recombinant Fusion Proteins; Microtubules; Kinetochores; Proteins; Drosophila Proteins; Animals; Kinetics; Green Fluorescent Proteins; Cyclin B; Fungal Proteins; Cell Cycle Proteins; Drosophila; Models, Biological; Centrosome; Luminescent Proteins; Point Mutation; Mitotic Spindle Apparatus; Saccharomyces cerevisiae Proteins