Functions of the Tumor Suppressor ING Family Genes

ING1 gene, the founding member of the ING tumor suppressor family, was originally identified through subtractive hybridization between normal mammary epithelial cells and breast cancer cell lines, and subsequent in vivo selection of genetic suppressor element that displayed oncogenic features. The four additional members of the ING family (ING2-5) were recently identified and all the gene products contain a highly conserved plant homeodomain (PHD) finger motif in the carboxy (C)-terminal end. Although exact functions of ING family genes have not been clarified, the gene products are involved in transcriptional regulation, apoptosis, cell cyle, angiogenesis and DNA repair through p53-dependent and -independent pathways and constituting complexes with histone acetyltransferases (HAT) and histone deacetylases (HDAC). This review summarizes the known biological functions of the ING tumor suppressors and signaling pathways that they involve.