Acts as a tumor suppressor in many tumor types; induces growth arrest or apoptosis depending on the physiological circumstances and cell type. Involved in cell cycle regulation as a trans-activator that acts to negatively regulate cell division by controlling a set of genes required for this process. One of the activated genes is an inhibitor of cyclin-dependent kinases. Apoptosis induction seems to be mediated either by stimulation of BAX and FAS antigen expression, or by repression of Bcl-2 expression. Its pro-apoptotic activity is activated via its interaction with PPP1R13B/ASPP1 or TP53BP2/ASPP2 (By similarity). However, this activity is inhibited when the interaction with PPP1R13B/ASPP1 or TP53BP2/ASPP2 is displaced by PPP1R13L/iASPP (By similarity). In cooperation with mitochondrial PPIF is involved in activating oxidative stress-induced necrosis; the function is largely independent of transcription. Prevents CDK7 kinase activity when associated to CAK complex in response to DNA damage, thus stopping cell cycle progression. Induces the transcription of long intergenic non-coding RNA p21 (lincRNA-p21) and lincRNA-Mkln1. LincRNA-p21 participates in TP53-dependent transcriptional repression leading to apoptosis and seems to have an effect on cell-cycle regulation. Regulates the circadian clock by repressing CLOCK-ARNTL/BMAL1-mediated transcriptional activation of PER2. Binds 1 zinc ion per subunit. Forms homodimers and homotetramers (By similarity). Binds DNA as a homotetramer. Interacts with AXIN1. Probably part of a complex consisting of TP53, HIPK2 and AXIN1. Interacts with histone acetyltransferases EP300 and methyltransferases HRMT1L2 and CARM1, and recruits them to promoters. Interacts (via C-terminus) with TAF1; when TAF1 is part of the TFIID complex. Interacts with ING4; this interaction may be indirect. Found in a complex with CABLES1 and TP73. Interacts with HIPK1, HIPK2, and TP53INP1. Interacts with WWOX. Interacts with USP7 and SYVN1. Interacts with HSP90AB1. Interacts with CHD8; leading to recruit histone H1 and prevent transactivation activity. Interacts with ARMC10, BANP, CDKN2AIP, NUAK1, STK11/LKB1, UHRF2 and E4F1. Interacts with YWHAZ; the interaction enhances TP53 transcriptional activity. Phosphorylation of YWHAZ inhibits this interaction. Interacts (via DNA-binding domain) with MAML1 (via N-terminus). Interacts with MKRN1. Interacts with PML (via C-terminus). Interacts with MDM2; leading to ubiquitination and proteasomal degradation of TP53. Directly interacts with FBXO42; leading to ubiquitination and degradation of TP53. Interacts (phosphorylated at Ser-15 by ATM) with the phosphatase PP2A-PPP2R5C holoenzyme; regulates stress-induced TP53-dependent inhibition of cell proliferation. Interacts with PPP2R2A. Interacts with AURKA, DAXX, BRD7 and TRIM24. Interacts (when monomethylated at Lys-380) with L3MBTL1. Interacts with GRK5. Binds to the CAK complex (CDK7, cyclin H and MAT1) in response to DNA damage. Interacts with CDK5 in neurons. Interacts with AURKB, SETD2, UHRF2 and NOC2L. Interacts (via N-terminus) with PTK2/FAK1; this promotes ubiquitination by MDM2. Interacts with PTK2B/PYK2; this promotes ubiquitination by MDM2. Interacts with PRKCG. Interacts with PPIF; the association implicates preferentially tetrameric TP53, is induced by oxidative stress and is impaired by cyclosporin A (CsA). Interacts with SNAI1; the interaction induces SNAI1 degradation via MDM2-mediated ubiquitination and inhibits SNAI1-induced cell invasion. Interacts with KAT6A. Interacts with UBC9. Interacts with ZNF385B; the interaction is direct. Interacts (via DNA-binding domain) with ZNF385A; the interaction is direct and enhances p53/TP53 transactivation functions on cell-cycle arrest target genes, resulting in growth arrest. Interacts with ANKRD2. Interacts with RFFL and RNF34; involved in p53/TP53 ubiquitination. Interacts with MTA1 and COP1. Interacts with CCAR2 (via N-terminus). Interacts with MORC3. Interacts (via C-terminus) with POU4F2 (via C-terminus). Interacts (via oligomerization region) with NOP53; the interaction is direct and may prevent the MDM2-mediated proteasomal degradation of TP53. Interacts with AFG1L; mediates mitochondrial translocation of TP53. Interacts with UBD. Interacts with TAF6. Interacts with C10orf90/FATS; the interaction inhibits binding of TP53 and MDM2 (By similarity). Interacts with NUPR1; interaction is stress-dependent. Forms a complex with EP300 and NUPR1; this complex binds CDKN1A promoter leading to transcriptional induction of CDKN1A (By similarity). Interacts with PRMT5 in response to DNA damage; the interaction is TTC5/STRAP dependent (By similarity). Interacts with PPP1R13L (via SH3 domain and ANK repeats); the interaction inhibits pro-apoptotic activity of p53/TP53 (By similarity). Interacts with PPP1R13B/ASPP1 and TP53BP2/ASPP2; the interactions promotes pro-apoptotic activity (By similarity). When phosphorylated at Ser-15, interacts with DDX3X and gamma-tubulin (By similarity). Interacts with KAT7/HBO1; leading to inhibit histone acetyltransferase activity of KAT7/HBO1 (By similarity). Interacts (via N-terminus) with E3 ubiquitin-protein ligase MUL1; the interaction results in ubiquitination of cytoplasmic TP53 at Lys-24 and subsequent proteasomal degradation (By similarity). Interacts with S100A4; this interaction promotes TP53 degradation (By similarity). Interacts with TTC5/STRAP; the interaction may result in increased mitochondrial-dependent apoptosis (By similarity). Interacts with NQO1; this interaction is NADH-dependent, stabilizes TP53 in response to oxidative stress and protects it from ubiquitin-independent degradation by the 20S proteasome. Interaction with BANP promotes nuclear localization. Recruited into PML bodies together with CHEK2. Translocates to mitochondria upon oxidative stress. Translocates to mitochondria in response to mitomycin C treatment (By similarity). The [KR]-[STA]-K motif is specifically recognized by the SETD7 methyltransferase. Phosphorylation on Ser residues mediates transcriptional activation. Phosphorylation at Ser-9 by HIPK4 increases repression activity on BIRC5 promoter (By similarity). Phosphorylated on Thr-18 by VRK1, which may prevent the interaction with MDM2. Phosphorylated on Ser-20 by CHEK2 in response to DNA damage, which prevents ubiquitination by MDM2. Phosphorylated on Ser-20 by PLK3 in response to reactive oxygen species (ROS), promoting p53/TP53-mediated apoptosis. Phosphorylated on Ser-33 by CDK7 in a CAK complex in response to DNA damage. Phosphorylated by HIPK1. Phosphorylated on Ser-46 by HIPK2 upon UV irradiation. Phosphorylation on Ser-46 is required for acetylation by CREBBP. Phosphorylated on Ser-390 following UV but not gamma irradiation. Stabilized by CDK5-mediated phosphorylation in response to genotoxic and oxidative stresses at Ser-15, Ser-33 and Ser-46, leading to accumulation of p53/TP53, particularly in the nucleus, thus inducing the transactivation of p53/TP53 target genes. Phosphorylated by DYRK2 at Ser-46 in response to genotoxic stress. Phosphorylated at Ser-313 and Ser-390 by CDK2 in response to DNA-damage (By similarity). Phosphorylation at Ser-15 is required for interaction with DDX3X and gamma-tubulin (By similarity). Ubiquitinated by MDM2 and SYVN1, which leads to proteasomal degradation. Ubiquitinated by RFWD3, which works in cooperation with MDM2 and may catalyze the formation of short polyubiquitin chains on p53/TP53 that are not targeted to the proteasome. Ubiquitinated by MKRN1 at Lys-289 and Lys-290, which leads to proteasomal degradation. Deubiquitinated by USP10, leading to stabilize it. Ubiquitinated by TRIM24, RFFL, RNF34 and RNF125, which leads to proteasomal degradation. Ubiquitination by TOPORS induces degradation. Deubiquitination by USP7, leading to stabilize it. Ubiquitinated by COP1, which leads to proteasomal degradation (By similarity). Ubiquitination and subsequent proteasomal degradation is negatively regulated by CCAR2 (By similarity). Polyubiquitinated by C10orf90/FATS, polyubiquitination is 'Lys-48'-linkage independent and non-proteolytic, leading to TP53 stabilization (By similarity). Monomethylated at Lys-370 by SETD7, leading to stabilization and increased transcriptional activation. Monomethylated at Lys-368 by SMYD2, leading to decreased DNA-binding activity and subsequent transcriptional regulation activity. Lys-370 monomethylation prevents interaction with SMYD2 and subsequent monomethylation at Lys-368. Dimethylated at Lys-371 by EHMT1 and EHMT2. Monomethylated at Lys-380 by KMT5A, promoting interaction with L3MBTL1 and leading to repress transcriptional activity. Demethylation of dimethylated Lys-368 by KDM1A prevents interaction with TP53BP1 and represses TP53-mediated transcriptional activation (By similarity). Monomethylated at Arg-331 and dimethylated at Arg-333 by PRMT5; methylation is increased after DNA damage and might possibly affect TP53 target gene specificity (By similarity). Polyubiquitinated by MUL1 at Lys-24 which leads to proteasomal degradation (By similarity). Sumoylated with SUMO1. Sumoylated at Lys-384 by UBC9 (By similarity). Acetylation of Lys-380 by CREBBP enhances transcriptional activity. Acetylation of Lys-380 by EP300. Deacetylation of Lys-380 by SIRT1 impairs its ability to induce proapoptotic program and modulate cell senescence. Deacetylation by SIRT2 impairs its ability to induce transcription activation in a AKT-dependent manner. Acetylation at Lys-379 increases stability. Deacetylation at Lys-379 by SIRT6 decreases its stability, thereby regulating cell senescence. p53 is found in increased amounts in a wide variety of transformed cells. p53 is frequently mutated or inactivated in many types of cancer. Belongs to the p53 family.