Research focus
Deregulation of ubiquitin-mediated proteolysis including the APC/C-ubiquitin system is increasingly understood to underlie genome instability. Genome instability is key to both the etiology and treatment of several human diseases. Greater understanding of APC/C function will therefore be of great benefit for human health. Although 20 years have passed since its discovery, our understanding of the APC/C function and control is lamentably limited. This is partly due to the sheer size and complexity of the enzyme. In fact, it was impossible to reconstitute apo-APC/C until recently. However, our latest development APC/C re-constitution using the MultiBac system will enable us to manipulate APC/C function at will and together with the Xenopus egg system, detailed analysis of the ‘dynamic regulation’ of vertebrate APC/Cs can be achieved to a level never attained before.

CDK1 and APC/C are two key regulatory enzymes controlling the cell division, growth, differentiation and death, through phosphorylation and ubiquitylation, respectively. Although it has long been apparent that phosphorylation modifies APC/C function, the challenges posed by the need for functional assays to study this control put the elucidation of molecular basis of phosphorylation control beyond our grasp. We recently overcame these limitations with a pipeline that uses reconstituted recombinant APC/C in Xenopus cell free extracts to show how CDK1 activates the APC/C through coordinated phosphorylation of Apc3 and Apc1 (Fujimitsu, K. et al., Science 2016). We will now extend this pipeline with targeted assays that will determine how phosphatases and APC/C binding proteins regulate these phosphorylation events.