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Inhibitor of growth (ING) domain of inhibitor of growth protein 1 (ING1) ING1 is an epigenetic regulator and a type II tumor suppressor that impacts cell growth, aging, apoptosis, and DNA repair, by affecting chromatin conformation and gene expression. It acts as a reader of the active chromatin mark, the trimethylation of histone H3 lysine 4 (H3K4me3). It binds and directs growth arrest and DNA damage inducible protein 45 a (Gadd45a) to target sites, thus linking the histone code with DNA demethylation. It interacts with the proliferating cell nuclear antigen (PCNA) via the PCNA-interacting protein (PIP) domain in a UV-inducible manner. It also interacts with a PCNA-interacting protein, p15 (PAF). Moreover, ING1 associates with members of the 14-3-3 family, which is necessary for the cytoplasmic relocalization. Endogenous ING1 protein specifically interacts with the pro-apoptotic BCL2 family member BAX and colocalizes with BAX in a UV-inducible manner. It stabilizes the p53 tumor suppressor by inhibiting polyubiquitination of multi-monoubiquitinated forms via interaction with and colocalization of the herpesvirus-associated ubiquitin-specific protease (HAUSP)-deubiquitinase with p53. It is also involved in trichostatin A-induced apoptosis and caspase 3 signaling in p53-deficient glioblastoma cells. In addition, tyrosine kinase Src can bind phosphorylate ING1 and further regulates its activity. ING1 contains an N-terminal leucine zipper-like (LZL) motif-containing ING domain, and a well-characterized C-terminal plant homeodomain (PHD)-type zinc-finger domain. |
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