Cul4A also has been implicated in the ubiquitination and proteolysis of tumour suppressors, such as p53 19, p21 20, p27 2, DLC1 21 and RASSF1A 22, and may contribute to tumorigenesis and cancer development through ubiquitination and then proteolysis of tumour suppressors. Here, CDKN1A is linked to cancer.