In the case of HDAC, the deacetylation of K16-H4 seems to be particularly closely regulated: in yeast, Sir2 deacetylates this residue, and its human homologue, Sirtuin 1 (SIRT1), also deacetylates the tumour-suppressor protein p53, thereby establishing another link with cancer. This evidence concerns the gene HDAC9 and cancer.