TP53 and cancer: [22] RBBP6 has been identified as a putative E3 ubiquitin ligase because of the presence of a RING finger domain. [8] Several major types of E3 enzymes (RING/U-box families) have been linked to the development of cancer. [23] The human RBBP6 contains domains that are known to interact with TP53 and its function as ubiquitin might cause the deregulation of TP53, which would then lead to carcinogenesis. [6] However, the correlation between RBBP6 and mutant TP53 has not been analyzed in human colon cancer.