ING1, also inhibitor of growth protein 1, is a 422 amino acid protein, which contains 1 PHD-type zinc finger and belongs to the ING family. ING1 localizes in the nucleus and interacts with TP53. It exsits as varous isoforms and isoform 1 is a 47 kDa protein. Isoform 2 is a 33 kDa protein and expressed in all normal tissues, as well as in all breast cancer and melanoma cell lines examined. ING1 cooperates with p53/TP53 in the negative regulatory pathway of cell growth by modulating p53-dependent transcriptional activation. It is implicated as a tumor suppressor gene.