Our research is focused on the structural analysis of proteins and its complexes in solution by nuclear magnetic resonance (NMR). NMR has the potential to determine the structure of the protein in solution, detect ligand binding, map the binding site and quantify the affinity of the interaction. We use this methodology to characterise and modulate protein-protein interactions involved in chromatin regulation and signalling.
Reading the histone code.
ING4, a member of the Inhibitor of Growth family of tumour suppressors, is a dimeric protein with a Plant HomeoDomain (PHD) which binds to histone-3 trimethylated at lysine 4. ING4 is less selective than ING2 towards recognition of K4 versus K9 methylated histone 3, and ING4 is also less selective towards the different methylation states of K4. ING4 might bind to unmodified and monomethylated histone 3 and prepare the K4 for further methylation. ING4 could be involved in transcription activation, since it participates in a Histone Acetyl transferase complex. A mutant in the PHD of ING4 identified in a cell line derived from lung cancer does nor arrest cell growth and has an increased affinity for unmodified histone 3 than the wild type.
DNA replication and repair.
PCNA (Proliferating Cell Nuclear Antigen) is an essential factor for DNA replication and repair and the effector through which several cell cycle control and apoptosis signals are realized. The assignment of the NMR spectrum of the 90 kDa homotrimeric PCNA sets the basis for a detailed analysis of the variety of interactions displayed by PCNA. We are investigating the interaction of PCNA with the proteins ING1 and GADD45 (Growth Arrest and DNA damage-inducible gene). ING1 has a PIP sequence motif (PCNA Interacting Protein). GADD45 does not have the PIP, which suggests that the binding of ING1 and GADD45 to PCNA is not mutually exclusive.