scholarly journals Definition of pRB- and p53-Dependent and -Independent Steps in HIRA/ASF1a-Mediated Formation of Senescence-Associated Heterochromatin Foci

2007 ◽  
Vol 27 (7) ◽  
pp. 2452-2465 ◽  
Author(s):  
Xiaofen Ye ◽  
Brad Zerlanko ◽  
Rugang Zhang ◽  
Neeta Somaiah ◽  
Marc Lipinski ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Histone Chaperone ◽  
Dominant Negative ◽  
Nuclear Bodies ◽  
P53 Tumor Suppressor ◽  
Pml Nuclear Bodies ◽  
Pml Bodies ◽  
Definition Of ◽  
Senescence Program

ABSTRACT Cellular senescence is an irreversible proliferation arrest triggered by short chromosome telomeres, activated oncogenes, and cell stress and mediated by the pRB and p53 tumor suppressor pathways. One of the earliest steps in the senescence program is translocation of a histone chaperone, HIRA, into promyelocytic leukemia (PML) nuclear bodies. This relocalization precedes other markers of senescence, including the appearance of specialized domains of facultative heterochromatin called senescence-associated heterochromatin foci (SAHF) and cell cycle exit. SAHF represses expression of proliferation-promoting genes, thereby driving exit from the cell cycle. HIRA bound to another histone chaperone, ASF1a, drives formation of SAHF. Here, we show that HIRA's translocation to PML bodies occurs in response to all senescence triggers tested. Dominant negative HIRA mutants that block HIRA's localization to PML bodies prevent formation of SAHF, as does a PML-RARα fusion protein which disrupts PML bodies, directly supporting the idea that localization of HIRA to PML bodies is required for formation of SAHF. Significantly, translocation of HIRA to PML bodies occurs in the absence of functional pRB and p53 tumor suppressor pathways. However, our evidence indicates that downstream of HIRA's localization to PML bodies, the HIRA/ASF1a pathway cooperates with pRB and p53 to make SAHF, with the HIRA/ASF1a and pRB pathways acting in parallel. We present evidence that convergence of the HIRA/ASF1a and pRB pathways occurs through a DNAJ-domain protein, DNAJA2.

scholarly journals ei24, a p53 Response Gene Involved in Growth Suppression and Apoptosis

2000 ◽  
Vol 20 (1) ◽  
pp. 233-241 ◽  
Author(s):  
Zhengming Gu ◽  
Cathy Flemington ◽  
Thomas Chittenden ◽  
Gerard P. Zambetti
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Apoptotic Cell ◽  
Functional Characterization ◽  
Growth Control ◽  
P53 Tumor Suppressor ◽  
Cycle Arrest ◽  
P53 Response

ABSTRACT DNA damage and/or hyperproliferative signals activate the wild-type p53 tumor suppressor protein, which induces a G1 cell cycle arrest or apoptosis. Although the mechanism of p53-mediated cell cycle arrest is fairly well defined, the p53-dependent pathway regulating apoptosis is poorly understood. Here we report the functional characterization of murine ei24 (also known asPIG8), a gene directly regulated by p53, whose overexpression negatively controls cell growth and induces apoptotic cell death. Ectopic ei24 expression markedly inhibits cell colony formation, induces the morphological features of apoptosis, and reduces the number of β-galactosidase-marked cells, which is efficiently blocked by coexpression of Bcl-XL. Theei24/PIG8 gene is localized on human chromosome 11q23, a region frequently altered in human cancers. These results suggest that ei24 may play an important role in negative cell growth control by functioning as an apoptotic effector of p53 tumor suppressor activities.

scholarly journals Demonstration of a RNA-dependent nuclear interaction between the promyelocytic leukaemia protein and glyceraldehyde-3-phosphate dehydrogenase

1998 ◽  
Vol 335 (3) ◽  
pp. 691-696 ◽  
Author(s):  
Graeme W. CARLILE ◽  
William G. TATTON ◽  
Katherine L. B. BORDEN
Keyword(s):  
Acute Promyelocytic Leukaemia ◽  
Neuronal Death ◽  
Nuclear Interaction ◽  
Nuclear Bodies ◽  
Promyelocytic Leukaemia ◽  
Pml Nuclear Bodies ◽  
Pml Bodies ◽  
Rnase Treatment ◽  
Rna Disruption ◽  
Apoptotic Neuronal Death

The promyelocytic leukaemia (protein) (PML) localizes to multiprotein complexes known as PML nuclear bodies. We found that glyceraldehyde-3-phosphate dehydrogenase (GAPDH) co-immunoprecipitates with PML and co-localizes with PML in nuclear bodies. RNase treatment disrupts the ability of PML and GAPDH to both co-localize and co-immunoprecipitate, indicating that the association between PML and GAPDH depends on the presence of RNA. Disruption of PML bodies contributes towards reduced apoptosis in acute promyelocytic leukaemia and GAPDH induces apoptotic neuronal death. The GAPDH–PML interaction may be involved in the regulation of apoptosis.

scholarly journals Nuclear and cytoplasmic shuttling of TRADD induces apoptosis via different mechanisms

2002 ◽  
Vol 157 (6) ◽  
pp. 975-984 ◽  
Author(s):  
Michael Morgan ◽  
Jacqueline Thorburn ◽  
Pier Paolo Pandolfi ◽  
Andrew Thorburn
Keyword(s):  
Nuclear Export ◽  
Tumor Necrosis Factor Receptor ◽  
Promyelocytic Leukemia ◽  
Dominant Negative ◽  
Nuclear Bodies ◽  
Death Domain ◽  
Apoptosis Pathway ◽  
Promyelocytic Leukemia Protein ◽  
Caspase Inhibitors ◽  
Pml Nuclear Bodies

The adapter protein tumor necrosis factor receptor (TNFR)1–associated death domain (TRADD) plays an essential role in recruiting signaling molecules to the TNFRI receptor complex at the cell membrane. Here we show that TRADD contains a nuclear export and import sequence that allow shuttling between the nucleus and the cytoplasm. In the absence of export, TRADD is found within nuclear structures that are associated with promyelocytic leukemia protein (PML) nuclear bodies. In these structures, the TRADD death domain (TRADD-DD) can activate an apoptosis pathway that is mechanistically distinct from its action at the membrane-bound TNFR1 complex. Apoptosis by nuclear TRADD-DD is promyelocytic leukemia protein dependent, involves p53, and is inhibited by Bcl-xL but not by caspase inhibitors or dominant negative FADD (FADD-DN). Conversely, apoptosis induced by TRADD in the cytoplasm is resistant to Bcl-xL, but sensitive to caspase inhibitors and FADD-DN. These data indicate that nucleocytoplasmic shuttling of TRADD leads to the activation of distinct apoptosis mechanisms that connect the death receptor apparatus to nuclear events.

PML mediates IFN-α–induced apoptosis in myeloma by regulating TRAIL induction

Blood ◽  
2005 ◽  
Vol 105 (3) ◽  
pp. 1280-1287 ◽  
Author(s):  
Chun Crowder ◽  
Øyvind Dahle ◽  
R. Eric Davis ◽  
Odd S. Gabrielsen ◽  
Stuart Rudikoff
Keyword(s):  
Multiple Myeloma ◽  
Dominant Negative ◽  
Nuclear Bodies ◽  
Myeloma Cells ◽  
Treatment Regimens ◽  
Pml Nuclear Bodies ◽  
Differential Responses ◽  
Nuclear Structures ◽  
Ifn Treatment ◽  
Induced Apoptosis

AbstractInterferon (IFN) induces expression of proapoptotic genes and has been used in the clinical treatment of multiple myeloma. The promyelocytic leukemia (PML) gene is an IFN-induced target that encodes a tumor suppressor protein. PML protein is typically localized within discrete speckled nuclear structures termed PML nuclear bodies (NBs). Multiple myeloma cells demonstrate differential responses to IFN treatment, the mechanism of which is largely unknown. Herein, we show that growth inhibition effects of IFN-α in myeloma cells correlate with PML NBs and tumor necrosis factor (TNF)–related apoptosis-inducing ligand (TRAIL) induction, whereas known IFN targets including signal transducer and activator of transcription-1 (STAT1), STAT3, p38, and Daxx cannot account for these differential responses. RNAi silencing of PML blocks IFN-α–induced apoptosis in myeloma cells and correspondingly down-regulates TRAIL expression. Similarly, stable expression of a dominant negative TRAIL receptor DR5 partially blocks IFN-induced cell death. These results demonstrate that PML and TRAIL play important roles in IFN-induced apoptosis and identify TRAIL as a novel downstream transcriptional target of PML. Identification of PML and PML NBs as effectors of IFN responses provides insights into mechanisms by which tumor cells exhibit resistance to this class of agents and may prove useful in assessing treatment regimens.

scholarly journals A dynamic connection between centromeres and ND10 proteins

1999 ◽  
Vol 112 (20) ◽  
pp. 3443-3454 ◽  
Author(s):  
R.D. Everett ◽  
W.C. Earnshaw ◽  
A.F. Pluta ◽  
T. Sternsdorf ◽  
A.M. Ainsztein ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Regulatory Protein ◽  
Nuclear Bodies ◽  
Interphase Nuclei ◽  
Pml Nuclear Bodies ◽  
Dynamic Cell ◽  
As Stress ◽  
Simplex Virus ◽  
External Stimuli

ND10, otherwise known as nuclear dots, PML nuclear bodies or PODs, are punctate foci in interphase nuclei that contain several cellular proteins. The functions of ND10 have not been well defined, but they are sensitive to external stimuli such as stress and virus infection, and they are disrupted in malignant promyelocytic leukaemia cells. Herpes simplex virus type 1 regulatory protein Vmw110 induces the proteasome-dependent degradation of ND10 component proteins PML and Sp100, particularly the species of these proteins which are covalently conjugated to the ubiquitin-like protein SUMO-1. We have recently reported that Vmw110 also induces the degradation of centromere protein CENP-C with consequent disruption of centromere structure. These observations led us to examine whether there were hitherto undetected connections between ND10 and centromeres. In this paper we report that hDaxx and HP1 (which have been shown to interact with CENP-C and Sp100, respectively) are present in a proportion of both ND10 and interphase centromeres. Furthermore, the proteasome inhibitor MG132 induced an association between centromeres and ND10 proteins PML and Sp100 in a significant number of cells in the G(2) phase of the cell cycle. These results imply that there is a dynamic, cell cycle regulated connection between centromeres and ND10 proteins which can be stabilised by inhibition of proteasome-mediated proteolysis.

A Stapled p53 Helix Targets HDMX to Overcome Nutlin-3 Resistance and Reactivate the p53 Tumor Suppressor Pathway in Cancer

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 2645-2645
Author(s):  
Federico Bernal ◽  
Mark Wade ◽  
Amy M. Silverstein ◽  
Gregory L. Verdine ◽  
Geoffrey M. Wahl ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Cancer Cells ◽  
Ubiquitin Ligase ◽  
Human Cancer ◽  
Transactivation Domain ◽  
Binding Interaction ◽  
P53 Tumor Suppressor ◽  
Cycle Arrest

Abstract p53 is a transcription factor that induces cell cycle arrest or apoptosis in response to DNA damage and cellular stress, and thereby plays a critical role in protecting cells from malignant transformation. The E3 ubiquitin ligase HDM2 controls p53 levels through a direct binding interaction that neutralizes the transactivation activity of p53 and targets it for degradation via the ubiquitylation-proteasomal pathway. Whereas the HDM2-homologue HDMX lacks ubiquitin ligase function, it participates in regulating the p53 axis by heterodimerizing with HDM2 and sequestering p53 through protein interaction. Loss of p53 activity, either by deletion, mutation, or HDM2/HDMX overexpression, is the most common defect in human cancer. Tumors expressing wild type p53 are rendered vulnerable by pharmacologic approaches that stabilize and upregulate p53. In this context, HDM2 and HDMX have emerged as independent therapeutic targets for restoring p53 activity and resensitizing cancer cells to apoptosis in vitro and in vivo. The small molecule nutlin-3 is an effective antagonist of the p53-HDM2 interaction. However, several studies have demonstrated the inability of nutlin-3 to disrupt the p53-HDMX complex, rendering tumor cells that overexpress HDMX nutlin-3-resistant. We have previously described the synthesis and characterization of a hydrocarbon-stapled alpha-helical p53 peptide (SAH-p53-8) that binds HDM2 with low nanomolar affinity, targets HDM2 in situ, and reactivates the p53 tumor suppressor pathway in HDM2-overexpressing osteosarcoma cells. We now report that SAH-p53-8 binds HDMX with even higher affinity, co-immunoprecipitates with endogenous HDMX, and induces apoptosis and cell cycle arrest in nutlin-3-resistant cancer cells that overexpress HDMX. Thus, by inserting a chemical staple into a peptide fragment of the p53 transactivation domain, we have generated the first bifunctional inhibitor of HDM2 and HDMX, enabling the investigation and pharmacologic modulation of both targets in human cancer.

scholarly journals mdm-2 inhibits the G1 arrest and apoptosis functions of the p53 tumor suppressor protein.

1996 ◽  
Vol 16 (5) ◽  
pp. 2445-2452 ◽  
Author(s):  
J Chen ◽  
X Wu ◽  
J Lin ◽  
A J Levine
Keyword(s):  
Cell Cycle ◽  
Tumor Suppressor ◽  
Cell Cycle Arrest ◽  
Biological Activities ◽  
Tumor Suppressor Protein ◽  
G1 Arrest ◽  
Physical Interaction ◽  
P53 Tumor Suppressor ◽  
Cycle Arrest ◽  
P53 Tumor Suppressor Protein

The mdm-2 gene encodes a 90-kDa polypeptide that binds specifically to the p53 tumor suppressor protein. This physical interaction results in the inhibition of the transcriptional functions of p53 (J. Chen, J. Lin, and A. J. Levine, Mol. Med. 1:142-152, 1995, and J. Momand, G. P. Zambetti, D. C. Olson, D. George, and A. J. Levine, Cell 69:1237-1245, 1992). Experiments are described that demonstrate the ability of mdm-2 to abrogate both the p53-mediated cell cycle arrest and the apoptosis functions. In addition, the results presented here suggest that mdm-2 binding to p53 and the resultant inhibition of p53 transcription functions are critical for reversing p53-mediated cell cycle arrest. The N-terminal half or domain of the mdm-2 protein is sufficient to regulate these biological activities of p53, consistent with the possibility that the highly conserved central acidic region and the C-terminal putative zinc fingers of mdm-2 may encode other functions.

scholarly journals Human Papillomavirus Oncoprotein E7 Targets the Promyelocytic Leukemia Protein and Circumvents Cellular Senescence via the Rb and p53 Tumor Suppressor Pathways

2005 ◽  
Vol 25 (3) ◽  
pp. 1013-1024 ◽  
Author(s):  
Oliver Bischof ◽  
Karim Nacerddine ◽  
Anne Dejean
Keyword(s):  
Tumor Suppressor ◽  
Cellular Senescence ◽  
Transcriptional Activation ◽  
Human Fibroblasts ◽  
Promyelocytic Leukemia ◽  
Human Papillomaviruses ◽  
Dominant Negative ◽  
Oncogenic Signaling ◽  
Promyelocytic Leukemia Protein ◽  
P53 Tumor Suppressor

ABSTRACT Cellular senescence can be triggered by a variety of signals, including loss of telomeric integrity or intense oncogenic signaling, and is considered a potent, natural tumor suppressor mechanism. Previously, it was shown that the promyelocytic leukemia protein (PML) induces cellular senescence when overexpressed in primary human fibroblasts. The mechanism by which the PML IV isoform elicits this irreversible growth arrest is believed to involve activation of the tumor suppressor pathways p21/p53 and p16/Rb; however, a requirement for either pathway has not been demonstrated unequivocally. To investigate the individual contributions of p53 and Rb to PML-induced senescence, we used oncoproteins E6 and E7 from human papillomaviruses (HPVs), which predominantly target p53 and Rb. We show that E7, but not E6, circumvents PML-induced senescence. Using different E7 mutant proteins, dominant negative cyclin-dependent kinase 4, and p16 RNA interference, we demonstrate that Rb-related and Rb-independent mechanisms of E7 are necessary for subversion of PML-induced senescence and we identify PML as a novel target for E7. Interaction between E7 and a functional prosenescence complex composed of PML, p53, and CBP perturbs transcriptional activation of p53, thus highlighting a significant effect also on the p53 tumor suppressor pathway. Given the importance of HPV in the pathogenesis of cervical cancer, our results warrant a more detailed analyses of PML in HPV infections.

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