TP53 regulates transcription of cell cycle genes (Homo sapiens)
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TP53 controls transcription of genes involved in both G1 and G2 cell cycle arrest. The most prominent TP53 target involved in G1 arrest is the inhibitor of cyclin-dependent kinases CDKN1A (p21). CDKN1A is one of the earliest genes induced by TP53 (El-Deiry et al. 1993). CDKN1A binds and inactivates CDK2 in complex with cyclin A (CCNA) or E (CCNE), thus preventing G1/S transition (Harper et al. 1993). Nevertheless, under prolonged stress, the cell destiny may be diverted towards an apoptotic outcome. For instance, in case of an irreversible damage, TP53 can induce transcription of an RNA binding protein PCBP4, which can bind and destabilize CDKN1A mRNA, thus alleviating G1 arrest and directing the affected cell towards G2 arrest and, possibly, apoptosis (Zhu and Chen 2000, Scoumanne et al. 2011). Expression of E2F7 is directly induced by TP53. E2F7 contributes to G1 cell cycle arrest by repressing transcription of E2F1, a transcription factor that promotes expression of many genes needed for G1/S transition (Aksoy et al. 2012, Carvajal et al. 2012). ARID3A is a direct transcriptional target of TP53 (Ma et al. 2003) that may promote G1 arrest by cooperating with TP53 in induction of CDKN1A transcription (Lestari et al. 2012). However, ARID3A may also promote G1/S transition by stimulating transcriptional activity of E2F1 (Suzuki et al. 1998, Peeper et al. 2002).<p>TP53 contributes to the establishment of G2 arrest by inducing transcription of GADD45A and SFN, and by inhibiting transcription of CDC25C. TP53 induces GADD45A transcription in cooperation with chromatin modifying enzymes EP300, PRMT1 and CARM1 (An et al. 2004). GADD45A binds Aurora kinase A (AURKA), inhibiting its catalytic activity and preventing AURKA-mediated G2/M transition (Shao et al. 2006, Sanchez et al. 2010). GADD45A also forms a complex with PCNA. PCNA is involved in both normal and repair DNA synthesis. The effect of GADD45 interaction with PCNA, if any, on S phase progression, G2 arrest and DNA repair is not known (Smith et al. 1994, Hall et al. 1995, Sanchez et al. 2010, Kim et al. 2013). SFN (14-3-3-sigma) is induced by TP53 (Hermeking et al. 1997) and contributes to G2 arrest by binding to the complex of CDK1 and CCNB1 (cyclin B1) and preventing its translocation to the nucleus. Phosphorylation of a number of nuclear proteins by the complex of CDK1 and CCNB1 is needed for G2/M transition (Chan et al. 1999). While promoting G2 arrest, SFN can simultaneously inhibit apoptosis by binding to BAX and preventing its translocation to mitochondria, a step involved in cytochrome C release (Samuel et al. 2001). TP53 binds the promoter of the CDC25C gene in cooperation with the transcriptional repressor E2F4 and represses CDC25C transcription, thus maintaining G2 arrest (St Clair et al. 2004, Benson et al. 2014).<p>Several direct transcriptional targets of TP53 are involved in cell cycle arrest but their mechanism of action is still unknown. BTG2 is induced by TP53, leading to cessation of cellular proliferation (Rouault et al. 1996, Duriez et al. 2002). BTG2 binds to the CCR4-NOT complex and promotes mRNA deadenylation activity of this complex. Interaction between BTG2 and CCR4-NOT is needed for the antiproliferative activity of BTG2, but the underlying mechanism has not been elucidated (Rouault et al. 1998, Mauxion et al. 2008, Horiuchi et al. 2009, Doidge et al. 2012, Ezzeddine et al. 2012). Two polo-like kinases, PLK2 and PLK3, are direct transcriptional targets of TP53. TP53-mediated induction of PLK2 may be important for prevention of mitotic catastrophe after spindle damage (Burns et al. 2003). PLK2 is involved in the regulation of centrosome duplication through phosphorylation of centrosome-related proteins CENPJ (Chang et al. 2010) and NPM1 (Krause and Hoffmann 2010). PLK2 is frequently transcriptionally silenced through promoter methylation in B-cell malignancies (Syed et al. 2006). Induction of PLK3 transcription by TP53 (Jen and Cheung 2005) may be important for coordination of M phase events through PLK3-mediated nuclear accumulation of CDC25C (Bahassi et al. 2004). RGCC is induced by TP53 and implicated in cell cycle regulation, possibly through its association with PLK1 (Saigusa et al. 2007). PLAGL1 (ZAC1) is a zinc finger protein directly transcriptionally induced by TP53 (Rozenfeld-Granot et al. 2002). PLAGL1 expression is frequently lost in cancer (Varrault et al. 1998) and PLAGL1 has been implicated in both cell cycle arrest and apoptosis (Spengler et al. 1997), but its mechanism of action remains unknown.<p>The zinc finger transcription factor ZNF385A (HZF) is a direct transcriptional target of TP53 that can form a complex with TP53 and facilitate TP53-mediated induction of CDKN1A and SFN (14-3-3 sigma) transcription (Das et al. 2007).<p>For a review of the role of TP53 in cell cycle arrest and cell cycle transcriptional targets of TP53, please refer to Riley et al. 2008, Murray-Zmijewski et al. 2008, Bieging et al. 2014, Kruiswijk et al. 2015. View original pathway at Reactome.</div>
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A:Cdk2:p21/p27
complexAfter deadenylation the mRNA is then hydrolyzed by either the 5' to 3' pathway or the 3' to 5' pathway. It is unknown what determinants target a mRNA to one pathway or the other.
The 5' to 3' pathway is initiated by binding of the Lsm1-7 complex to the 3' oligoadenylate tail followed by decapping by the DCP1-DCP2 complex. The 5' to 3' exoribonuclease XRN1 then hydrolyzes the remaining RNA.
The 3' to 5' pathway is initiated by the exosome complex at the 3' end of the mRNA. The exosome processively hydrolyzes the mRNA from 3' to 5', leaving only a capped oligoribonucleotide. The cap is then removed by the scavenging decapping enzyme DCPS.
1. "Multidomain" BAX family proteins such as BAX, BAK etc. that display sequence conservation in their BH1-3 regions. These proteins act downstream in mitochondrial disruption.
2. "BH3-only" proteins such as BID,BAD, NOXA, PUMA,BIM, and BMF have only the short BH3 motif. These act upstream in the pathway, detecting developmental death cues or intracellular damage. Anti-apoptotic members like Bcl-2, Bcl-XL and their relatives exhibit homology in all segments BH1-4. One of the critical functions of BCL-2/BCL-XL proteins is to maintain the integrity of the mitochondrial outer membrane.
During early G1, cells can enter a quiescent G0 state. In quiescent cells, the evolutionarily conserved DREAM complex, consisting of the pocket protein family member p130 (RBL2), bound to E2F4 or E2F5, and the MuvB complex, represses transcription of cell cycle genes (reviewed by Sadasivam and DeCaprio 2013).
During early G1 phase in actively cycling cells, transcription of cell cycle genes is repressed by another pocket protein family member, p107 (RBL1), which forms a complex with E2F4 (Ferreira et al. 1998, Cobrinik 2005). RB1 tumor suppressor, the product of the retinoblastoma susceptibility gene, is the third member of the pocket protein family. RB1 binds to E2F transcription factors E2F1, E2F2 and E2F3 and inhibits their transcriptional activity, resulting in prevention of G1/S transition (Chellappan et al. 1991, Bagchi et al. 1991, Chittenden et al. 1991, Lees et al. 1993, Hiebert 1993, Wu et al. 2001). Once RB1 is phosphorylated on serine residue S795 by Cyclin D:CDK4/6 complexes, it can no longer associate with and inhibit E2F1-3. Thus, CDK4/6-mediated phosphorylation of RB1 leads to transcriptional activation of E2F1-3 target genes needed for the S phase of the cell cycle (Connell-Crowley et al. 1997). CDK2, in complex with cyclin E, contributes to RB1 inactivation and also activates proteins needed for the initiation of DNA replication (Zhang 2007). Expression of D type cyclins is regulated by extracellular mitogens (Cheng et al. 1998, Depoortere et al. 1998). Catalytic activities of CDK4/6 and CDK2 are controlled by CDK inhibitors of the INK4 family (Serrano et al. 1993, Hannon and Beach 1994, Guan et al. 1994, Guan et al. 1996, Parry et al. 1995) and the Cip/Kip family, respectively.
In unstressed cells, TP53 protein levels are low due to MDM2-mediated ubiquitination of TP53, which triggers proteasome-mediated degradation. In response to stress, TP53 undergoes stabilizing phosphorylation, mainly at serine residues S15 and S20. Several different kinases can phosphorylate TP53 at these sites, but the main S15 kinases are considered to be ATM and ATR, while the main S20 kinases are considered to be CHEK2 and CHEK1. Additional phosphorylation of TP53 at serine residue S46 promotes transcription of pro-apoptotic, rather than cell cycle arrest genes.
Acetylation mainly has a positive impact on transcriptional activity of TP53, while methylation can both positively and negatively regulate TP53.
Some posttranslational modifications regulate interaction of TP53 with transcriptional co-factors, some of which are themselves transcriptional targets of TP53.
For review of the complex network of TP53 regulation, please refer to Kruse and Gu 2009, and Meek and Anderson 2009.
Transcription of
Cell Death GenesPro-apoptotic transcriptional targets of TP53 involve TRAIL death receptors TNFRSF10A (DR4), TNFRSF10B (DR5), TNFRSF10C (DcR1) and TNFRSF10D (DcR2), as well as the FASL/CD95L death receptor FAS (CD95). TRAIL receptors and FAS induce pro-apoptotic signaling in response to external stimuli via extrinsic apoptosis pathway (Wu et al. 1997, Takimoto et al. 2000, Guan et al. 2001, Liu et al. 2004, Ruiz de Almodovar et al. 2004, Liu et al. 2005, Schilling et al. 2009, Wilson et al. 2013). IGFBP3 is a transcriptional target of TP53 that may serve as a ligand for a novel death receptor TMEM219 (Buckbinder et al. 1995, Ingermann et al. 2010).
TP53 regulates expression of a number of genes involved in the intrinsic apoptosis pathway, triggered by the cellular stress. Some of TP53 targets, such as BAX, BID, PMAIP1 (NOXA), BBC3 (PUMA) and probably BNIP3L, AIFM2, STEAP3, TRIAP1 and TP53AIP1, regulate the permeability of the mitochondrial membrane and/or cytochrome C release (Miyashita and Reed 1995, Oda et al. 2000, Samuels-Lev et al. 2001, Nakano and Vousden 2001, Sax et al. 2002, Passer et al. 2003, Bergamaschi et al. 2004, Li et al. 2004, Fei et al. 2004, Wu et al. 2004, Park and Nakamura 2005, Patel et al. 2008, Wang et al. 2012, Wilson et al. 2013). Other pro-apoptotic genes, either involved in the intrinsic apoptosis pathway, extrinsic apoptosis pathway or pyroptosis (inflammation-related cell death), which are transcriptionally regulated by TP53 are cytosolic caspase activators, such as APAF1, PIDD1, and NLRC4, and caspases themselves, such as CASP1, CASP6 and CASP10 (Lin et al. 2000, Robles et al. 2001, Gupta et al. 2001, MacLachlan and El-Deiry 2002, Rikhof et al. 2003, Sadasivam et al. 2005, Brough and Rothwell 2007).
It is uncertain how exactly some of the pro-apoptotic TP53 targets, such as TP53I3 (PIG3), RABGGTA, BCL2L14, BCL6, NDRG1 and PERP contribute to apoptosis (Attardi et al. 2000, Guo et al. 2001, Samuels-Lev et al. 2001, Contente et al. 2002, Ihrie et al. 2003, Bergamaschi et al. 2004, Stein et al. 2004, Phan and Dalla-Favera 2004, Jen and Cheung 2005, Margalit et al. 2006, Zhang et al. 2007, Saito et al. 2009, Davies et al. 2009, Giam et al. 2012).
TP53 is stabilized in response to cellular stress by phosphorylation on at least serine residues S15 and S20. Since TP53 stabilization precedes the activation of cell death genes, the TP53 tetramer phosphorylated at S15 and S20 is shown as a regulator of pro-apoptotic/pro-cell death genes. Some pro-apoptotic TP53 target genes, such as TP53AIP1, require additional phosphorylation of TP53 at serine residue S46 (Oda et al. 2000, Taira et al. 2007). Phosphorylation of TP53 at S46 is regulated by another TP53 pro-apoptotic target, TP53INP1 (Okamura et al. 2001, Tomasini et al. 2003). Additional post-translational modifications of TP53 may be involved in transcriptional regulation of genes presented in this pathway and this information will be included as evidence becomes available.
Activation of some pro-apoptotic TP53 targets, such as BAX, FAS, BBC3 (PUMA) and TP53I3 (PIG3) requires the presence of the complex of TP53 and an ASPP protein, either PPP1R13B (ASPP1) or TP53BP2 (ASPP2) (Samuels-Lev et al. 2001, Bergamaschi et al. 2004, Patel et al. 2008, Wilson et al. 2013), indicating how the interaction with specific co-factors modulates the cellular response/outcome.
TP53 family members TP63 and or TP73 can also activate some of the pro-apoptotic TP53 targets, such as FAS, BAX, BBC3 (PUMA), TP53I3 (PIG3), CASP1 and PERP (Bergamaschi et al. 2004, Jain et al. 2005, Ihrie et al. 2005, Patel et al. 2008, Schilling et al. 2009, Celardo et al. 2013).
For a review of the role of TP53 in apoptosis and pro-apoptotic transcriptional targets of TP53, please refer to Riley et al. 2008, Murray-Zmijewski et al. 2008, Bieging et al. 2014, Kruiswijk et al. 2015.
Tetramer:ARID3A
GeneTetramer:PLAGL1
GeneAnnotated Interactions
A:Cdk2:p21/p27
complexTetramer:ARID3A
GeneTetramer:ARID3A
GeneTetramer:PLAGL1
GeneTetramer:PLAGL1
Gene