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PHD finger found in inhibitor of growth protein 4 (ING4) and 5 (ING5) ING4, also termed p29ING4, and ING5, also termed p28ING5, belong to the inhibitor of growth (ING) family of type II tumor suppressors. ING4 acts as an E3 ubiquitin ligase to induce ubiquitination of the p65 subunit of NF-kappaB and inhibit the transactivation of NF-kappaB target genes. It also induces apoptosis through a p53 dependent pathway, including increasing p53 acetylation, inhibiting Mdm2-mediated degradation of p53 and enhancing the expression of p53 responsive genes both at the transcriptional and post-translational levels. Moreover, ING4 can inhibit the translation of proto-oncogene MYC by interacting with AUF1. It also regulates other transcription factors, such as hypoxia-inducible factor (HIF). ING5 is a Tip60 cofactor that acetylates p53 at K120 and subsequently activates the expression of p53-dependent apoptotic genes in response to DNA damage. Aberrant ING5 expression may contribute to pathogenesis, growth, and invasion of gastric carcinomas and colorectal cancer. ING5 can physically interact with p300 and p53 in vivo, and its overexpression induces apoptosis in colorectal cancer cells. It also associates with cyclin A1 (INCA1) and functions as a growth suppressor with suppressed expression in Acute Myeloid Leukemia (AML). Moreover, ING5 translocation from the nucleus to the cytoplasm might be a critical event for carcinogenesis and tumor progression in human head and neck squamous cell carcinoma. Both ING4 and ING5 contain an N-terminal ING histone-binding domain and a C-terminal plant homeodomain (PHD) finger. They associate with histone acetyltransferase (HAT) complexes containing MOZ (monocytic leukemia zinc finger protein)/MORF (MOZ-related factor) and HBO1, and further direct the MOZ/MORF and HBO1 complexes to chromatin. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",