Centrosomes have a role in regulating the destruction of cyclin B in early Drosophila embryos.
We reported previously that the disappearance of cyclin B at the end of mitosis in early Drosophila embryos starts at centrosomes and spreads into the spindle [1]. Here, we used a novel mutation, centrosome fall off (cfo), to investigate whether centrosomes are required to initiate the disappearance of cyclin B from the spindle. In embryos laid by homozygous cfo mutant mothers, the centrosomes co-ordinately detached from the mitotic spindle during mitosis, and the centrosomeless spindles arrested at anaphase. Cyclin B levels decreased on the detached centrosomes, but not on the arrested centrosomeless spindles, presumably explaining why the spindles arrest in anaphase in these embryos. We found that the expression of a non-degradable cyclin B in embryos also caused an anaphase arrest, but most centrosomes remained attached to the arrested spindles, and non-degradable cyclin B levels remained high on both the centrosomes and spindles. These findings suggest that the disappearance of cyclin B from centrosomes and spindles is closely linked to its destruction, and that a connection between centrosomes and spindles is required for the proper destruction of the spindle-associated cyclin B in early Drosophila embryos. These results may have important implications for the mechanism of the spindle-assembly checkpoint, as they suggest that unattached kinetochores may arrest cells in mitosis, at least in part, by signalling to centrosomes to block the initiation of cyclin B destruction.
Wakefield
J G
JG
Wellcome/CRC Institute and Department of Genetics, University of Cambridge, Cambridge, UK.
Huang
J Y
JY
Raff
J W
JW
D000705:Anaphase; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism; D018385:Centrosome / Q000378:metabolism*; D019926:Cyclin B / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000378:metabolism*; D005260:Female; D017930:Genes, Reporter; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D008941:Spindle Apparatus / Q000378:metabolism*
C503698:CycB protein, Drosophila; D019926:Cyclin B; D029721:Drosophila Proteins; D011993:Recombinant Fusion Proteins