细胞周期调控示意图  (点击信号分子查询相关抗体)

In particular, we are interested in CDK4 and CDK6, which associate with the D-type cyclins to control progression through the G1 phase of the cell cycle by phosphorylation of the tumour suppressor protein, pRb. Our interest in these specific CDKs stems from the fact that we now know that most human cancers contain mutations that affect CDK4, CDK6, the D-type cyclins, their regulators or pRB itself. In addition, these kinases act as a key integration point between extracellular signalling pathways and the cell cycle. For example, both the Ras and Wnt signalling pathways can regulate cyclin D1 expression. Thus, understanding the molecular basis of the CDK/cyclin/pRb pathway and its regulation will be important in the identification of novel targets for new cancer treatments.

Our main approach has been to focus on the CDK4/cyclin D1 complex and how it is regulated at the molecular level. One particular strategy has been to investigate regulation of cyclin D1 turnover and through these studies we have identified a pathway that can regulate cyclin D1 turnover in response to DNA damage, which we are now investigating further. Our discoveries from these studies has also led us to become interested in cell cycle checkpoints that are activated in response to DNA damage, and in particular how these may signal to CDKs, especially CDK4/cyclin D1, to cause cell cycle arrest. Potential players in these pathways are the cell cycle checkpoint kinases Chk1 and Chk2 and their upstream regulators, ATM and ATR. We are also looking at the effects of different cellular conditions on CDK4/cyclin D1 kinase activity, including DNA damage. One finding from this work has been the identification of a novel kinase activity that can phosphorylate CDK4 at tyrosine 17, which is currently being isolated in the laboratory.

Another aspect of our work is the opportunity to take part in the initiation and implementation of cancer drug screens. An example of this is the cell-based screen for inhibitors of pRb phosphorylation that we have developed in collaboration with Sibylle Mittnacht (see Sibylle Mittnacht's research entry) of the Cancer Research UK Centre for Cell and Molecular Biology and the Analytical Technology and Screening Team within our Centre. Phosphorylation of the tumour suppressor protein pRb during G1 by CDKs is essential for G1 progression and as mentioned above, most human cancers contain genetic alterations in at least one member of this pathway that lead to inappropriate phosphorylation of pRb and deregulation of its activity. We have therefore developed a high through-put cellular assay to screen for small molecule inhibitors of pRb phosphorylation that can attenuate this deregulation. This screen is now complete and we are in the process of decovolution/.target identification for a number of hits. More recently we have been involved in the initiation of biochemical drug screens for a number of cell cycle kinases including Chk1 and Chk2 and are developing cellular assays so that we may investigate the mechanism of action of hits from these screens.