p16INK4A (p16) is a critical regulator of the mammalian cell-cycle that is found to be mutated in many cancers. Accumulation of p16 leads to senescence and is a molecular marker of cellular ageing. We have found that under oxidizing conditions, the single cysteine residue of p16 forms an intermolecular disulfide bond. Formation of the disulfide-linked dimer leads to a dramatic structural rearrangement of the protein, from an all alpha-helical structure, to beta‑sheet amyloid fibrils.1 Conversion to amyloid fibril structures prevents p16 from carrying out its normal function as a kinase inhibitor, and therefore p16 amyloid formation may be a novel regulatory mechanism of p16 activity. We are currently investigating the structure and formation mechanism of p16 amyloid fibrils, using liquid and solid-state NMR, fluorescence assays and mass spectrometry. We are also investigating how cancer-associated mutations may alter p16 amyloid formation. These findings will give insight into a novel disulfide-linked amyloid structure, as well as highlighting their potential role in cancer and cell division mechanisms.