Participates in the apoptotic response to DNA damage. Isoforms containing the transactivation domain are pro-apoptotic, isoforms lacking the domain are anti-apoptotic and block the function of p53 and transactivating p73 isoforms. May be a tumor suppressor protein. Is an activator of FOXJ1 expression, essential for the positive regulation of lung ciliated cell differentiation (PubMed:26947080). 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, HIPK2, RANBP9 and WWOX (By similarity). Interacts (via SAM domain) with FBXO45 (via B30.2/SPRY domain) (By similarity). Interacts with YAP1 (phosphorylated form) (By similarity). Interacts with HCK (via SH3 domain); this inhibits TP73 activity and degradation (By similarity). Interacts (via SAM domain) with NQO1; this interaction is NADH-dependent, stabilizes TP73 in response to oxidative stress and protects it from ubiquitin-independent degradation by the 20S proteasome. Accumulates in the nucleus in response to DNA damage. Found in striatal neurons of mutant huntingtin (htt) transgenic mice (at protein level). Isoform 1 is expressed in the nasal epithelium, the vomeronasal organ, the hippocampus and the hypothalamus. 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. Sumoylated on Lys-622, which potentiates proteasomal degradation but does not affect transcriptional activity. Phosphorylation by PLK1 and PLK3 inhibits the transcription regulator activity and pro-apoptotic function (By similarity). Higher levels of phosphorylation seen in striatal neurons of. mutant huntingtin (htt) transgenic mice. Polyubiquitinated by RCHY1/PIRH2; leading to its degradation by the proteasome. Mice lacking Tp73 display a runting phenotype and high rates of mortality due to massive gastrointestinal hemorrhages or intracranial bleeding. The gastrointestinal tract suffers loss of enterocytes and excessive mucosecretions in the duodenum, ileum and cecum. Survivors exhibit hippocampal dysgenesis, hydrocephalus, chronic infections and inflammation, as well as abnormalities in pheromone sensory pathways. Activated and stabilized by interaction with RANBP9. Produced by alternative promoter usage. Produced by alternative splicing of isoform 2. Produced by alternative splicing of isoform 2. Belongs to the p53 family. Extended N-terminus.