I retired from the University in October 2007. This account summarises my work up to that time and during 2007/2008. Our research interests have focused on protein kinases, their regulation and their roles in the cell cycle and in transcription. Electron microscope studies on phosphorylase kinase are described in Dr Vénien-Bryan’s section.

P-TEFb (CDK9/cyclin T) promotes mRNA transcriptional elongation through phosphorylation of elongation repressors and RNA polymerase II. In order to understand the regulation of a transcriptional CDK by its cognate cyclin we have determined the structure of the CDK9/cyclin T1 (CDK9/CycT1) (Baumli et al, 2008). There are distinct differences between CDK9/CycT1 and the cell cycle CDK, CDK2/CycA, manifested by a relative rotation of 26° of CycT1 with respect to the CDK, showing for the first time plasticity in CDK cyclin interactions (Figure 1). Flavopiridol is an anti-cancer drug in Phase II clinical trials for chronic lymphocytic leukemia and other cancers. Structural studies showed that flavopiridol bound to the ATP site of CDK9 inducing unanticipated structural changes that bury the inhibitor, providing specificity and potency (Figure 2). CDK9 activity and recognition of regulatory proteins is governed by autophosphorylation. We have shown that CDK9/CycT1 cis autophosphorylates on Thr186 in the activation segment and three C-terminal phosphorylation sites. CDK9/CycT1 studies are continuing by Dr Baumli to visualise the higher order complexes involved in regulation of CDK9/CycT1, including 7SK RNA and HEXIM1, and consideration for modifications to flavopiridol in order to modulate its affinity for serum proteins while retaining high affinity for CDK9. The current status of protein kinase structures and compounds approved for clinical use is summarised in a recent review (Johnson, 2008).

The eukaryotic cell cycle involves replication of the genetic material and the cell's biomass to yield two duplicate daughter cells. Progression through the cycle is driven by the sequential activities of different cyclin dependent protein kinases (CDKs). The organisation of both the temporal and spatial events is characterised by selection of the right substrates by the protein kinases. CDK2/cyclin E governs entry into S phase during which DNA replication takes place. Levels of cyclin E are elevated in breast cancers. Structural studies on CDK2/cyclin E have given an explanation for some of its important cell properties (Honda et al., 2005). With CDK2/cyclin A we have sought to understand how the binding of a substrate at a remote site from the catalytic site can influence substrate specificity (Cheng et al 2006) (Figure 3). This has led to an investigation of how the different cyclins confer substrate specificity on their kinases. We have shown that although CDK2/cyclin A and CDK2/cyclin E have very similar properties the association of CDK2 with cyclin B confers different substrate recognition properties that are related to the role of cyclin B in mitosis (Brown, NR et al. Cell Cycle, 2007).

Genetic studies have implicated a number of factors that either predispose for or protect against alcoholism. The ALDH2*2 gene encoding the inactive variant form of the mitochondrial aldehyde dehydrogenase (ALDH2) protects nearly all carriers of this gene from alcoholism. Inhibition of the normal variant ALDH2 has hence become a possible strategy for the treatment of alcoholism. The structure determination of ALDH2 in complex with the natural product daidzin, the active principle in a herbal remedy for “alcohol addiction” provides a lead for the design of ALDH2 inhibitors with improved pharmacokinetic properties (Lowe et al., 2008).