Function
Tumor suppressor that is required to sustain G2/M checkpoint after DNA damage. Acts as a p53/TP53 activator by inhibiting MDM2 binding to p53/TP53 and stimulating non-proteolytic polyubiquitination of p53/TP53. Exhibits ubiquitin ligase activity and assemble ubiquitin polymers through 'Lys-11'- , 'Lys-29'- and 'Lys-63'- -linkages, independently of the ubiquitin-conjugating enzyme. Promotes p53/TP53-dependent transcription of CDKN1A/p21, leading to robust checkpoint response. Mediates CDKN1A/p21 protein stability in a ubiquitin-independent manner. Interacts with HDAC1 and prevents binding of HDAC1 to CDKN1A/p21 and facilitates the acetylation and stabilization of CDKN1A/p21. May have a role in the assembly of primary cilia.
