Fig. 3. Both CDK1 phosphorylation sites are required for localisation of Cdc27 to mitotic chromosomes. (A,B) Confocal images from GFP::Cdc27^P304A transgenic syncytial embryos at various stages of mitosis (B) showed no significant differences in dynamic localisation to the wild-type GFP::Cdc27 transgenic line (A). An identical result was seen with the GFP::Cdc27^P456A single point mutant (not shown). However the fusion protein containing mutations in both potential Cdk1 phosphorylation sites (GFP::Cdc27^P304A,P456A) was no longer found localised to the chromosomes during mitosis (C). White open arrowheads indicate the nuclear envelope membrane localised with fusion proteins (bright ring structures) in A,B,D in prophase and metaphase images. It is less abundant in C, white open arrows indicate the mitotic chromosomes regions; GFP fusion proteins in white associate with chromosomes in A and B; and do not associate with chromosomes (shadow regions) in C,D. Double white open arrowheads show the mid-body regions at anaphase and telophase. A, panels 1-4, merged confocal images (GFP::Cdc27 in green, Rhodamine-H1-labelled chromosomes in red); A, panels 5-8: Rhodamine-H1-labelled chromosomes in white. Bar, 10 µm.