Participates in the apoptotic response to DNA damage. May be a tumor suppressor protein (By similarity). Is an activator of FOXJ1 expression, essential for the positive regulation of lung ciliated cell differentiation (By similarity). Binds 1 zinc ion per subunit. Found in a complex with p53/TP53 and CABLES1. The C-terminal oligomerization domain binds to the ABL1 tyrosine kinase SH3 domain. Interacts with HECW2. Isoforms Alpha and Beta interact with HIPK2. Isoform Alpha interacts with RANBP9. Interacts with WWOX (By similarity). Isoform Beta interacts homotypically and with p53, whereas isoform Alpha does not. Interacts (via SAM domain) with FBXO45 (via B30.2/SPRY domain) (By similarity). Interacts with YAP1 (phosphorylated form). Interacts with HCK (via SH3 domain); this inhibits TP73 activity and degradation (By similarity). Accumulates in the nucleus in response to DNA damage. Possesses an acidic transactivation domain, a central DNA binding domain and a C-terminal oligomerization domain that binds to the ABL1 tyrosine kinase SH3 domain. The PPxY motif mediates interaction with WWOX. Isoform Alpha (but not isoform Beta) is sumoylated on Lys-628, which potentiates proteasomal degradation but does not affect transcriptional activity. Polyubiquitinated by RCHY1/PIRH2; leading to its degradation by the proteasome. Activated and stabilized by interaction with RANBP9. Belongs to the p53 family.