The inhibitor of growth (ING2) tumor suppressor is implicated in oncogenesis, DNA repair, growth regulation and apoptosis. ING2 negatively regulates cell proliferation by enhancing acetylation of p53, a major tumor suppressor, which is mutated in about half of all human cancers. Our preliminary studies indicate that the PHD finger of ING2 specifically recognizes the histone tail domains and inositol hexakisphosphate (IP6) messenger revealing a novel link between IP6-mediated signaling and chromatin regulation. However, the molecular mechanisms underlying ING2 function have not been established. The structural basis of the histone and IP6 recognition remains unexplored and the effect of IP6 interaction on ING2 targeting to nucleosomes is not known. ? ? This project focuses on structural characterization of the histone and IP6 binding, novel functions of the PHD domain. The hypotheses to be tested are: (1) ING2 is targeted to nucleosomes through the interaction of PHD with histone tails and (2) nucleosome recruitment of lNG2 is negatively regulated by IP6 binding. ? ? The atomic-resolution structures of ING2 PHD bound to the H4 histone tail peptide and IP6 will be determined by multidimensional heteronuclear NMR or by X-ray crystallography. The binding site residues will be mutated and the mutant proteins will be tested in vitro by NMR and pull-down experiments and in vivo by fluorescence microscopy. The association of ING2 with nucleosomes will be investigated using electrophoretic mobility shift assays. To determine the specificity, interactions with unmodified and modified histone tail peptides and with other IPs will be analyzed by NMR, surface plasmon resonance and fluorescence spectroscopy. Functional significance of the histone and IP6 binding for p53 activation and apoptosis will be investigated. ? ? The results generated in this research will offer comprehensive understanding of the molecular mechanisms by which tumor suppressor ING2 is targeted to chromatin, interacts with IPs and regulates function of p53. These studies will aid in deeper understanding of how the critical ING2-p53 pathways can be therapeutically manipulated and may help to identify new diagnostic markers and targets to prevent and treat cancer. ? ?
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| RamÃrez, Julita; Dege, Carissa; Kutateladze, Tatiana G et al. (2012) MBD2 and multiple domains of CHD4 are required for transcriptional repression by Mi-2/NuRD complexes. Mol Cell Biol 32:5078-88 |
| Musselman, Catherine A; Kutateladze, Tatiana G (2011) Handpicking epigenetic marks with PHD fingers. Nucleic Acids Res 39:9061-71 |
| Mansfield, Robyn E; Musselman, Catherine A; Kwan, Ann H et al. (2011) Plant homeodomain (PHD) fingers of CHD4 are histone H3-binding modules with preference for unmodified H3K4 and methylated H3K9. J Biol Chem 286:11779-91 |
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