The cell cycle describes the process of cellular reproduction that primarily consists of duplication and segregation of genomic DNA. While being the universal minimal unit of heredity, the cell cycle must coordinate with cellular differentiation and organogenesis to form and maintain the body of the multicellular organism. Naturally, the collapse of such coordination leads to dysfunctional organs and cancer development.We aim to uncover how the cell cycle is coupled to cell fate determination and organ development in development and cancer using a multicellular model, Drosophila melanogaster (fruit fly). As a key component of such coordination machinery, we focus on the anaphase promoting complex/cyclosome (APC/C), a multisubunit ubiquitin ligase known to target numerous molecules for ubiquitin-mediated proteolysis during the cell cycle progression. A large body of evidence highlights the involvement of the APC/C in cellular differentiation and tissue functions. We are investigating the roles of the APC/C in the following two aspects.
1. Cell cycle control of developmental signalling pathways
It has come to light that various cell cycle regulators directly regulate developmental signalling pathways in order to coordinate cell fates with cell proliferation. We have recently found the evidence that the APC/C may regulate Wingless (Wg)/Wnt signalling through the destruction of a centrosomal kinase Nek2 during Drosophila eye development. We will extend this study by elucidating:
- Molecular basis of the cell cycle regulation of the Wg/Wnt pathway by the APC/C-Nek2 axis
- In vivoregulation of APC/C-dependent Wg regulation
- The role of the APC/C-Nek2 axis in Wnt regulation in human cells and colorectal cancer
In this project, we are collaborating with Marc de la Roche (Department of Biochemistry) and Andrew Fry (University of Leicester).
2. Coupling the centrosome cycle to the cell cycle
The centrosome is a gigantic organelle present in most animal cells that is critically important for faithful cell division, asymmetric cell division and developmental signalling. The centrosome organises microtubules to direct cell division and control cell shape and migration, thereby providing cells with directional and spatial regulation during development. Importantly, dysregulation of centrosomes is associated with various developmental diseases. In particular, over-amplified centrosomes are known as a hallmark of cancer. The APC/C is localised at the centrosome and controls the levels of some critical centrosome components, pointing to its pivotal role in the control of the centrosome. In the collaboration with David Glover’s group, we are investigating physical interactions between the APC/C and the centrosome by performing proteomic analysis of APC/C and centrosome components. In parallel, we are also conducting a series of biochemical and cell-based screenings of Drosophila centrosome components to identify centrosomal APC/C substrates. By characterising and manipulating the proteins identified, we are assessing the functions of the interactions and proteolysis on centrosome regulations and cell proliferation.
In this project, we are collaborating with David Glover (Department of Genetics), Hiro Yamano (UCL Cancer Institute), Renata Basto (Institute Curie) and Sofia Arujo (IBMB-CSIC, Barcellona).
3. Investigation into the mechanism of the cell cycle exit upon differentiation
We also investigate the mechanism of “cell cycle exit” that often precedes or coincides with terminal differentiation and cellular quiescence. The APC/C co-activator, Fzr/Cdh1, is essential for timely cell cycle exit and differentiation of neurons and various animal tissues. Utilising Drosophila eye imaginal discs as a model tissue we aim to determine the precise order of the molecular events that take place upon differentiation. We have been conducting a gain-of-function and loss-of-function genetic screen to identify the genes capable of inducing cell cycle exit in this tissue. In parallel, we have been performing tissue-specific proteomic analysis to characterise potential molecular interactions between the cell cycle regulators and developmental signalling molecules. We also aim to create reporters for key G1 phase cell cycle regulators including the APC/C to follow their dynamic behaviour by time-lapse analysis in single cells.
- Martins T, Meghini F, Florio F, Kimata Y. The APC/C coordinates retinal differentiation with G1 arrest through the Nek2-dependent modulation of Wingless signalling. Developmental Cell. 2017 Jan. online publication Dec 2016.
- Meghini F, Martins T, Tait X (equally contributed), Fujimitsu K, Yamano H, Glover DM, Kimata Y. Targeting of Fzr/Cdh1 for timely activation of the APC/C at the centrosome during mitotic exit. Nature Comms. 2016 Aug 25;7:12607.
- Haider S, Lipinszki Z, Przewloka MR, Ladak Y, D’Avino PP, Kimata Y, Lio’ P, Glover DM. DAPPER: a data-mining resource for protein-protein interactions. BioData Min. 2015 Sep 24;8:30.
- Kimata Y, Kitamura K, Fenner N, Yamano H. Mes1 controls the meiosis I to meiosis II transition by distinctly regulating the anaphase-promoting complex/cyclosome coactivators Fzr1/Mfr1 and Slp1 in fission yeast. Mol Biol Cell. 2011 May; 22(9):1486-9
- Kimata Y, Baxter JE, Fry AM, Yamano H. A role for the Fizzy/Cdc20 family of proteins in activation of the APC/C distinct from substrate recruitment. Mol Cell. 2008 Nov 21; 32(4):576-83
- Kimata Y, Trickey M, Izawa D, Gannon J, Yamamoto M, Yamano H. A mutual inhibition between APC/C and its substrate Mes1 required for meiotic progression in fission yeast. Dev Cell. 2008 Mar; 14(3):446-54
- Hayes MJ, Kimata Y (equally contributed), Wattam SL, Lindon C, Mao G, Yamano H, Fry AM. Early mitotic degradation of Nek2A depends on Cdc20-independent interaction with the APC/C. Nat Cell Biol. 2006 Jun; 8(6):607-14