ING1: ProductsING1 (Inhibitor of Growth 1; also p33ING1b and ING1A) is a 32 kDa member of the ING family of tumor suppressors. It is very widely expressed, and participates in multiple cell functions. When bound to p53, ING1 inhibits cell growth; when complexed to GADD45, ING1 enhances DNA nucleotide excision repair; and when associated with HAT, ING1 promotes hyperacetylation of histones H3 and H4. Human ING1 is 279 amino acids (aa) in length. It contains a PIP-PBD region (aa 5 - 45), an NLS (aa 142 - 158), and a plant homeodomain (PHD) (aa 210 - 259). Phosphorylation occurs on Ser126 and Ser199. There are at least three isoform variants. p47ING1a contains a 190 aa substitution for aa 1 - 46, p27ING1d shows a deletion of aa 2 - 45, and p24ING1c has an alternate start site at Met70. Over aa 213 - 327, human ING1 shares 82% aa identity with mouse ING1.