Cryo-EM structure of the CDK2-cyclin A-CDC25A complex.

The cell division cycle 25 phosphatases CDC25A, B and C regulate cell cycle transitions by dephosphorylating residues in the conserved glycine-rich loop of CDKs to activate their activity. Here, we present the cryo-EM structure of CDK2-cyclin A in complex with CDC25A at 2.7 Å resolution, providing a detailed structural analysis of the overall complex architecture and key protein-protein interactions that underpin this 86 kDa complex.

Crystallographic fragment screening in academic cancer drug discovery.

Fragment-based drug discovery (FBDD) has brought several drugs to the clinic, notably to target proteins once considered to be challenging, or even undruggable. Screening in FBDD relies upon observing and/or measuring weak (millimolar-scale) binding events using biophysical techniques or crystallographic fragment screening. This latter structural approach provides no information about binding affinity but can reveal binding mode and atomic detail on protein-fragment interactions to accelerate hit-to-lead development.

An open-source molecular builder and free energy preparation workflow.

Automated free energy calculations for the prediction of binding free energies of congeneric series of ligands to a protein target are growing in popularity, but building reliable initial binding poses for the ligands is challenging. Here, we introduce the open-source FEgrow workflow for building user-defined congeneric series of ligands in protein binding pockets for input to free energy calculations. For a given ligand core and receptor structure, FEgrow enumerates and optimises the bioactive conformations of the grown functional group(s), making use of hybrid machine learning/molecular mechanics potential energy functions where possible.

Targeting Mre11 overcomes platinum resistance and induces synthetic lethality in XRCC1 deficient epithelial ovarian cancers.

Platinum resistance is a clinical challenge in ovarian cancer. Platinating agents induce DNA damage which activate Mre11 nuclease directed DNA damage signalling and response (DDR). Upregulation of DDR may promote chemotherapy resistance.

FEN1 Blockade for Platinum Chemo-Sensitization and Synthetic Lethality in Epithelial Ovarian Cancers.

FEN1 plays critical roles in long patch base excision repair (LP-BER), Okazaki fragment maturation, and rescue of stalled replication forks. In a clinical cohort, FEN1 overexpression is associated with aggressive phenotype and poor progression-free survival after platinum chemotherapy. Pre-clinically, FEN1 is induced upon cisplatin treatment, and nuclear translocation of FEN1 is dependent on physical interaction with importin β.

Discriminative SKP2 Interactions with CDK-Cyclin Complexes Support a Cyclin A-Specific Role in p27KIP1 Degradation.

The SCF ubiquitin ligase relieves G1 checkpoint control of CDK-cyclin complexes by promoting p27KIP1 degradation. We describe reconstitution of stable complexes containing SKP1-SKP2 and CDK1-cyclin B or CDK2-cyclin A/E, mediated by the CDK regulatory subunit CKS1. We further show that a direct interaction between a SKP2 N-terminal motif and cyclin A can stabilize SKP1-SKP2-CDK2-cyclin A complexes in the absence of CKS1.

Chatterboxes: the structural and functional diversity of cyclins.

Proteins of the cyclin family have divergent sequences and execute diverse roles within the cell while sharing a common fold: the cyclin box domain. Structural studies of cyclins have played a key role in our characterization and understanding of cellular processes that they control, though to date only ten of the 29 CDK-activating cyclins have been structurally characterized by X-ray crystallography or cryo-electron microscopy with or without their cognate kinases. In this review, we survey the available structures of human cyclins, highlighting their molecular features in the context of their cellular roles.

Paradoxical activation of the protein kinase-transcription factor ERK5 by ERK5 kinase inhibitors.

The dual protein kinase-transcription factor, ERK5, is an emerging drug target in cancer and inflammation, and small-molecule ERK5 kinase inhibitors have been developed. However, selective ERK5 kinase inhibitors fail to recapitulate ERK5 genetic ablation phenotypes, suggesting kinase-independent functions for ERK5. Here we show that ERK5 kinase inhibitors cause paradoxical activation of ERK5 transcriptional activity mediated through its unique C-terminal transcriptional activation domain (TAD).

The diverse structural landscape of quadruplexes.

G-quadruplexes are secondary structures formed in G-rich sequences in DNA and RNA. Considerable research over the past three decades has led to in-depth insight into these unusual structures in DNA. Since the more recent exploration into RNA G-quadruplexes, such structures have demonstrated their in cellulo existence, function and roles in pathology.

Relative Binding Energies Predict Crystallographic Binding Modes of Ethionamide Booster Lead Compounds.

Transcriptional repressor EthR from Mycobacterium tuberculosis is a valuable target for antibiotic booster drugs. We previously reported a virtual screening campaign to identify EthR inhibitors for development. Two ligand binding orientations were often proposed, though only the top scoring pose was utilized for filtering of the large data set.

Differences in the Conformational Energy Landscape of CDK1 and CDK2 Suggest a Mechanism for Achieving Selective CDK Inhibition.

Dysregulation of the cell cycle characterizes many cancer subtypes, providing a rationale for developing cyclin-dependent kinase (CDK) inhibitors. Potent CDK2 inhibitors might target certain cancers in which CCNE1 is amplified. However, current CDK2 inhibitors also inhibit CDK1, generating a toxicity liability.

Probing biological activity through structural modelling of ligand-receptor interactions of 2,4-disubstituted thiazole retinoids.

Retinoids, such as all-trans-retinoic acid (ATRA), regulate cellular differentiation and signalling pathways in chordates by binding to nuclear retinoic acid receptors (RARα/β/γ). Polar interactions between receptor and ligand are important for binding and facilitating the non-polar interactions and conformational changes necessary for RAR-mediated transcriptional regulation. The constraints on activity and RAR-type specificity with respect to the structural link between the polar and non-polar functions of synthetic retinoids are poorly understood.

New active leads for tuberculosis booster drugs by structure-based drug discovery.

The transcriptional repressor EthR from Mycobacterium tuberculosis, a member of the TetR family of prokaryotic homo-dimeric transcription factors, controls the expression of the mycobacterial mono-oxygenase EthA. EthA is responsible for the bio-activation of the second-line tuberculosis pro-drug ethionamide, and consequently EthR inhibitors boost drug efficacy. Here, we present a comprehensive in silico structure-based screening protocol that led to the identification of a number of novel scaffolds of EthR inhibitors in subsequent biophysical screening by thermal shift assay.

Structural and docking studies of potent ethionamide boosters.

Tuberculosis remains the second only to HIV as the leading cause of death by infectious disease worldwide, and was responsible for 1.4 million deaths globally in 2011. One of the essential drugs of the second-line antitubercular regimen is the prodrug ethionamide, introduced in the 1960s.