Browse
Submit Data
Databases
API
Help

Dataset Information

11 Views

0 Connections

0 Citations

0 Reanalyses

0 Downloads

Omics score: 0

Differential regulation of the proapoptotic multidomain protein Bak by p53 and p73 at the promoter level.

ABSTRACT: During apoptosis Bcl-2 proteins control permeabilization of the mitochondrial outer membrane leading to the release of cytochrome c. Essential gatekeepers for cytochrome c release are the proapoptotic multidomain proteins, Bax, and Bak. The expression of Bax is upregulated upon cellular stress by the tumor suppressor p53. Despite the high functional homology of Bax and Bak, little is known about how the bak gene is regulated. To investigate its transcriptional regulation in further detail, we have analyzed a region spanning 8200 bp upstream of the bak start codon (within exon 2) for transcription factor-binding sites, and identified three p53 consensus sites (BS1-3). Reporter gene assays in combination with site-directed mutagenesis revealed that only one putative p53-binding site (BS3) is necessary and sufficient for induction of reporter gene expression by p53. Consistently, p53 induces expression of endogenous Bak. At the mRNA level, induction of Bak expression is weaker than induction of Puma and p21. Interestingly, Bak expression can also be induced by p73 that binds however to each of the three p53-binding sites within the bak promoter region. Our data suggest that expression of Bak can be induced by both, p53 and p73 utilizing different binding sites within the bak promoter.

SUBMITTER: Graupner V

PROVIDER: S-EPMC3131957 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Json Xml

Similar Datasets

The multidomain proapoptotic molecules Bax and Bak are directly activated by heat.

Project description:During apoptosis, engagement of the mitochondrial pathway involves a decisive event characterized by the release of mitochondrial intermembrane space proteins, such as cytochrome c. This permeabilization of the mitochondrial outer membrane depends on activation and oligomerization of multidomain Bcl-2-family proteins Bax or Bak. Although specific members of the Bcl-2 family can activate these proapoptotic proteins, we found that heat directly activated Bax or Bak to induce cytochrome c release. A preparation of mitochondria heated at 43 degrees C released cytochrome c in association with Bak oligomerization, and Bcl-xL prevented these events. Similarly, heat induced the oligomerization of recombinant Bax, conferring an ability to permeabilize mitochondria. Compared with wild-type cells, bax(-/-)bak(-/-) mouse embryonic fibroblasts and mitochondria isolated from these cells were resistant to heat-induced cytochrome c release. Cytosol from untreated cells inhibited heat-activated Bax or Bak; however, depletion of cytosolic Bcl-xL ablated this protection. Although mitochondria heated in the presence of cytosol did not release cytochrome c, they displayed a dramatic increase in sensitivity to permeabilization by the BH3-only protein Bid. Additionally, a peptide corresponding to the BH3 domain of Puma counteracted the inhibitory effect of cytosol and permitted heat-activated Bak to permeabilize the mitochondria. Therefore, heat represents a condition under which multidomain proapoptotic proteins are activated, and this activation is regulated by both antiapoptotic and BH3-only members of the Bcl-2 family. Our results support an emerging paradigm, wherein the activation of Bax or Bak and the blockade of antiapoptotic Bcl-2 proteins are pivotal steps in the mitochondrial pathway of apoptosis.

| S-EPMC1312392 | biostudies-literature

Direct activation of full-length proapoptotic BAK.

Project description:Proapoptotic B-cell lymphoma 2 (BCL-2) antagonist/killer (BAK) and BCL-2-associated X (BAX) form toxic mitochondrial pores in response to cellular stress. Whereas BAX resides predominantly in the cytosol, BAK is constitutively localized to the outer mitochondrial membrane. Select BCL-2 homology domain 3 (BH3) helices activate BAX directly by engaging an ?1/?6 trigger site. The inability to express full-length BAK has hampered full dissection of its activation mechanism. Here, we report the production of full-length, monomeric BAK by mutagenesis-based solubilization of its C-terminal ?-helical surface. Recombinant BAK autotranslocates to mitochondria but only releases cytochrome c upon BH3 triggering. A direct activation mechanism was explicitly demonstrated using a liposomal system that recapitulates BAK-mediated release upon addition of BH3 ligands. Photoreactive BH3 helices mapped both triggering and autointeractions to the canonical BH3-binding pocket of BAK, whereas the same ligands crosslinked to the ?1/?6 site of BAX. Thus, activation of both BAK and BAX is initiated by direct BH3-interaction but at distinct trigger sites. These structural and biochemical insights provide opportunities for developing proapoptotic agents that activate the death pathway through direct but differential engagement of BAK and BAX.

| S-EPMC3600461 | biostudies-literature

Proapoptotic Bax and Bak proteins form stable protein-permeable pores of tunable size.

Project description:The Bcl-2 proapoptotic proteins Bax and Bak mediate the permeabilization of the mitochondrial outer membrane during apoptosis. Current models consider that Bax and Bak form pores at the mitochondrial outer membrane that are responsible for the release of cytochrome c and other larger mitochondrial apoptotic factors (i.e. Smac/DIABLO, AIF, and endoglycosidase G). However, the properties and nature of Bax/Bak apoptotic pores remain enigmatic. Here, we performed a detailed analysis of the membrane permeabilizing activity of Bax and Bak at the single vesicle level. We directly visualized that cBid-activated Bax and Bak?C21 can form membrane pores large enough to release not only cytochrome c, but also allophycocyanine, a protein of 104 kDa. Interestingly, the size of Bax and Bak?C21 pores is not constant, as typically observed in purely proteinaceous channels, but evolves with time and depends on protein concentration. We found that Bax and Bak?C21 formed long-lived pores, whose areas changed with the amount of Bax/Bak?C21 but not with cardiolipin concentration. Altogether, our results demonstrate that Bax and Bak?C21 follow similar mechanisms of membrane permeabilization characterized by the formation of protein-permeable pores of dynamic size, in agreement with the proteolipidic nature of these apoptotic pores.

| S-EPMC3829170 | biostudies-literature

Regulation of transactivation-independent proapoptotic activity of p53 by FOXO3a.

Project description:The tumor suppressor p53 can trigger cell death independently of its transcriptional activity through subcellular translocation and activation of proapoptotic Bcl-2 family members. The regulation of such activity of endogenous p53 in response to stress remains largely unknown. Here we show that nuclear, activated FOXO3a could impair p53 transcriptional activity. However, activation of FOXO3a either on serum starvation or by expressing a constitutively active form of FOXO3a could induce p53-dependent apoptosis, even in cells bearing a transcriptionally inactive form of p53. Furthermore, FOXO3a could promote p53 cytoplasmic accumulation by increasing its association with nuclear exporting machinery. Our data also suggest that PUMA and Bax are required for p53-dependent apoptosis in manner that is independent of p53 transcriptional activity.

| S-EPMC1482564 | biostudies-literature

Structural basis for proapoptotic activation of Bak by the noncanonical BH3-only protein Pxt1.

Project description:Bak is a critical executor of apoptosis belonging to the Bcl-2 protein family. Bak contains a hydrophobic groove where the BH3 domain of proapoptotic Bcl-2 family members can be accommodated, which initiates its activation. Once activated, Bak undergoes a conformational change to oligomerize, which leads to mitochondrial destabilization and the release of cytochrome c into the cytosol and eventual apoptotic cell death. In this study, we investigated the molecular aspects and functional consequences of the interaction between Bak and peroxisomal testis-specific 1 (Pxt1), a noncanonical BH3-only protein exclusively expressed in the testis. Together with various biochemical approaches, this interaction was verified and analyzed at the atomic level by determining the crystal structure of the Bak-Pxt1 BH3 complex. In-depth biochemical and cellular analyses demonstrated that Pxt1 functions as a Bak-activating proapoptotic factor, and its BH3 domain, which mediates direct intermolecular interaction with Bak, plays a critical role in triggering apoptosis. Therefore, this study provides a molecular basis for the Pxt1-mediated novel pathway for the activation of apoptosis and expands our understanding of the cell death signaling coordinated by diverse BH3 domain-containing proteins.

| S-EPMC10298792 | biostudies-literature

Effect of hydroxyurea on the promoter occupancy profiles of tumor suppressor p53 and p73.

Project description:The p53 tumor suppressor and its related protein, p73, share a homologous DNA binding domain, and mouse genetics studies have suggested that they have overlapping as well as distinct biological functions. Both p53 and p73 are activated by genotoxic stress to regulate an array of cellular responses. Previous studies have suggested that p53 and p73 independently activate the cellular apoptotic program in response to cytotoxic drugs. The goal of this study was to compare the promoter-binding activity of p53 and p73 at steady state and after genotoxic stress induced by hydroxyurea.We employed chromatin immunoprecipitation, the NimbleGen promoter arrays and a model-based algorithm for promoter arrays to identify promoter sequences enriched in anti-p53 or anti-p73 immunoprecipitates, either before or after treatment with hydroxyurea, which increased the expression of both p53 and p73 in the human colon cancer cell line HCT116-3(6). We calculated a model-based algorithm for promoter array score for each promoter and found a significant correlation between the promoter occupancy profiles of p53 and p73. We also found that after hydroxyurea treatment, the p53-bound promoters were still bound by p73, but p73 became associated with additional promoters that that did not bind p53. In particular, we showed that hydroxyurea induces the binding of p73 but not p53 to the promoter of MLH3, which encodes a mismatch repair protein, and causes an up-regulation of the MLH3 mRNA.These results suggest that hydroxyurea exerts differential effects on the promoter-binding functions of p53 and p73 and illustrate the power of model-based algorithm for promoter array in the analyses of promoter occupancy profiles of highly homologous transcription factors.

| S-EPMC2711048 | biostudies-literature

RASSF1A elicits apoptosis through an MST2 pathway directing proapoptotic transcription by the p73 tumor suppressor protein.

Project description:RASSF1A is a tumor suppressor gene that is epigenetically silenced in a wide variety of sporadic human malignancies. Expression of alternative RASSF1 isoforms cannot substitute for RASSF1A-promoted cell-cycle arrest and apoptosis. Apoptosis can be driven by either activating Bax or by activation of MST kinases. The Raf1 proto-oncogene binds to MST2, preventing its activation and proapoptotic signaling. Here we show that key steps in RASSF1A-induced apoptosis are the disruption of the inhibitory Raf1-MST2 complex by RASSF1A and the concomitant enhancement of MST2 interaction with its substrate, LATS1. Subsequently, RASSF1A-activated LATS1 phosphorylates and releases the transcriptional regulator YAP1, allowing YAP1 to translocate to the nucleus and associate with p73, resulting in transcription of the proapoptotic target gene puma. Our results describe an MST2-dependent effector pathway for RASSF1A proapoptotic signaling and indicate that silencing of RASSF1A in tumors removes a proapoptotic signal emanating from p73.

| S-EPMC2821687 | biostudies-literature

p53/p73 Protein Network in Colorectal Cancer and Other Human Malignancies.

Project description:The p53 tumor suppressor protein is crucial for cell growth control and the maintenance of genomic stability. Later discovered, p63 and p73 share structural and functional similarity with p53. To understand the p53 pathways more profoundly, all family members should be considered. Each family member possesses two promoters and alternative translation initiation sites, and they undergo alternative splicing, generating multiple isoforms. The resulting isoforms have important roles in carcinogenesis, while their expression is dysregulated in several human tumors including colorectal carcinoma, which makes them potential targets in cancer treatment. Their activities arise, at least in part, from the ability to form tetramers that bind to specific DNA sequences and activate the transcription of target genes. In this review, we summarize the current understanding of the biological activities and regulation of the p53/p73 isoforms, highlighting their role in colorectal tumorigenesis. The analysis of the expression patterns of the p53/p73 isoforms in human cancers provides an important step in the improvement of cancer therapy. Furthermore, the interactions among the p53 family members which could modulate normal functions of the canonical p53 in tumor tissue are described. Lastly, we emphasize the importance of clinical studies to assess the significance of combining the deregulation of different members of the p53 family to define the outcome of the disease.

| S-EPMC8227208 | biostudies-literature

Functional association between Wwox tumor suppressor protein and p73, a p53 homolog.

Project description:The WWOX gene is a recently cloned tumor suppressor gene that spans the FRA16D fragile region. Wwox protein contains two WW domains that are generally known to mediate protein-protein interaction. Here we show that Wwox physically interacts via its first WW domain with the p53 homolog, p73. The tyrosine kinase, Src, phosphorylates Wwox at tyrosine 33 in the first WW domain and enhances its binding to p73. Our results further demonstrate that Wwox expression triggers redistribution of nuclear p73 to the cytoplasm and, hence, suppresses its transcriptional activity. In addition, we show that cytoplasmic p73 contributes to the proapoptotic activity of Wwox. Our findings reveal a functional cross-talk between p73 and Wwox tumor suppressor protein.

| S-EPMC384759 | biostudies-literature

Autoinhibitory regulation of p73 by Delta Np73 to modulate cell survival and death through a p73-specific target element within the Delta Np73 promoter.

Project description:p73 is a p53-related tumor suppressor but is also induced by oncogene products such as E2F-1, raising a question as to whether p73 is a tumor suppressor gene or oncogene. Unlike p53, p73 has several variants, including Delta Np73, which lacks the NH(2)-terminal transactivation domain. Although, in developing neurons, Delta Np73 is expressed abundantly and seems to inhibit the proapoptotic function of p53, the role of p73 and Delta Np73 and their regulatory mechanism in cell growth and differentiation are poorly understood. Here we report that p73, but not p53, directly activates the transcription of endogenous Delta Np73 by binding to the p73-specific target element located at positions -76 to -57 within the Delta Np73 promoter region. The activation of Delta Np73 promoter by p63 was marginal. Delta Np73 was associated with p73 alpha, p73 beta, and p53, as demonstrated by immunoprecipitation assays, and inhibited their transactivation activities when we used reporters of Mdm2, Bax, or Delta Np73 itself in SAOS-2 cells. Furthermore, induction or overexpression of Delta Np73 promoted cell survival by competing with p53 and p73 itself. Thus, our results suggest that the negative feedback regulation of p73 by its target Delta Np73 is a novel autoregulatory system for modulating cell survival and death.

| S-EPMC133713 | biostudies-literature

OmicsDI is part of the ELIXIR infrastructure

OmicsDI is an Elixir interoperability service. Learn more ›

Tweets

OmicsDI Databases

PRIDE
PeptideAtlas
MassIVE
JPOST Repository
Physiome Model Repository

EGA
EVA
ENA
LINCS
PAXDB
Cell Collective

MetaboLights
Metabolomics Workbench
MetabolomeExpress
GNPS
BioModels
FAIRDOMHub

ArrayExpress
dbGaP
ExpressionAtlas
GEO
NODE

Information

Databases
Help
API
Contact us
Code on GitHub
Terms of use
Submit Data