Flowchart: Preparation: P53

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Text Box: P53                                                        

 

 

Text Box: P21Cancer:

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Text Box: P73Text Box: Cdk2Text Box: Bcl2Smocking

Stem cell

 

2010/5/11  

 

Cell Stem Cell. 2010 Nov 5;7(5):606-17.

Mdm2 is required for survival of hematopoietic stem cells/progenitors via dampening of ROS-induced p53 activity.

Abbas HA, Maccio DR, Coskun S, Jackson JG, Hazen AL, Sills TM, You MJ, Hirschi KK, Lozano G.

Program in Genes and Development of The Graduate School of Biomedical Sciences, University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.

Abstract

Mdm2 is an E3 ubiquitin ligase that targets p53 for degradation. p53(515C) (encoding p53R172P) is a hypomorphic allele of p53 that rescues the embryonic lethality of Mdm2(-/-) mice. Mdm2(-/-) p53(515C/515C) mice, however, die by postnatal day 13 resulting from hematopoietic failure. Hematopoietic stem cells and progenitors of Mdm2(-/-) p53(515C/515C) mice were normal in fetal livers but were depleted in postnatal bone marrows. After birth, these mice had elevated reactive oxygen species (ROS) thus activating p53R172P. In the absence of Mdm2, stable p53R172P induced ROS and cell cycle arrest, senescence, and cell death in the hematopoietic compartment. This phenotype was partially rescued with antioxidant treatment and upon culturing of hematopoietic cells in methycellulose at 3% oxygen. p16 was also stabilized because of ROS, and its loss increased cell cycling and partially rescued hematopoiesis and survival. Thus, Mdm2 is required to control ROS-induced p53 levels for sustainable hematopoiesis.

Copyright © 2010 Elsevier Inc. All rights reserved.

J Immunol. 1995 Apr 15;154(8):3732-41.

Inhibition of stem cell factor-induced proliferation of primitive murine hematopoietic progenitor cells signaled through the 75-kilodalton tumor necrosis factor receptor. Regulation of c-kit and p53 expression.

Jacobsen FW, Dubois CM, Rusten LS, Veiby OP, Jacobsen SE.

Department of Immunology, Norwegian Radium Hospital, Oslo.

Abstract

TNF-alpha is a pleiotropic cytokine with stimulatory as well as inhibitory effects on hematopoiesis. We have previously demonstrated that TNF-alpha directly inhibits CSF-induced proliferation of primitive murine lineage-negative bone marrow progenitors (Lin-) and stem cell antigen-1 hematopoietic progenitors through the 75-kDa TNF receptor (TNF-R2), whereas TNF-alpha-induced inhibition of more committed Lin- progenitors is mediated through the 55-kDa TNF-R (TNF-R1), indicating a differential role of the two TNF-Rs in hematopoiesis. Numerous studies have demonstrated the ability of stem cell factor (SCF), a key regulator of hematopoiesis signaling through c-kit, to synergize with other hematopoietic growth factors, but little is known about cytokines capable of inhibiting hematopoiesis induced by SCF. While TNF-alpha has been demonstrated to enhance SCF-induced proliferation of myeloid leukemia blasts, the present report demonstrates that TNF-alpha, by signaling through TNF-R2, inhibits SCF-induced proliferation of normal murine Lin- and stem cell antigen-1 hematopoietic progenitors. SCF-stimulated proliferation of the hematopoietic cell line FDC-P1 was also potently inhibited by TNF-alpha and was accompanied by down-regulation of c-kit cell surface expression as well as c-kit mRNA levels. Finally, treatment of the FDC-P1 cell line with TNF-alpha resulted in increased levels of the tumor suppressor p53 mRNA, suggesting another mechanism by which hematopoietic effects of TNF-alpha may be mediated.

PMID: 7535812 [PubMed - indexed

Cancer Cell. 2002 Jun;1(5):493-503.

p53 stabilization is decreased upon NFkappaB activation: a role for NFkappaB in acquisition of resistance to chemotherapy.

Tergaonkar V, Pando M, Vafa O, Wahl G, Verma I.

Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, California 92037, USA.

Abstract

Chemotherapeutic agents simultaneously induce transcription factors p53 and NFkappaB. p53 induction can activate an apoptotic program, and resistance to chemotherapy correlates with the loss of a functional p53 pathway. By contrast, NFkappaB prevents apoptosis in response to chemotherapeutic agents. We have analyzed the p53 response in IKK1/2(-/-) MEFs, which lack detectable NFkappaB activity. Compared to WT fibroblasts, IKK1/2(-/-) fibroblasts showed increased cell death and p53 induction in response to the chemotherapeutic agent, doxorubicin. Reconstitution of IKK2, but not IKK1, increased Mdm2 levels and decreased doxorubicin-induced p53 stabilization and cell death. IKK2-mediated effects required its kinase function and were abrogated by coexpression of the dominant negative IkappaBalphaM, implying a role for NFkappaB in blocking chemotherapy-induced p53 and cell death.

PMID: 12124178 [PubMed - indexed for MEDLINE]

2009 Feb 24;106(8):2629-34. Epub 2009 Feb 5.

Phosphorylation of p53 by IkappaB kinase 2 promotes its degradation by beta-TrCP.

Xia Y, Padre RC, De Mendoza TH, Bottero V, Tergaonkar VB, Verma IM.

Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.

Abstract

Functional inactivation of p53 and constitutive activation of the NF-kappaB pathway has been associated with several human cancers. In this study, we show that IkappaB kinase 2 (IKK2/IKKbeta), which is critical for NF-kappaB activation, also phosphorylates p53. Phosphorylation of p53 at serines 362 and 366 by IKK2 leads to its recruitment to and ubiquitination by beta-TrCP1. Degradation of ubiquitinated p53 is independent of Mdm2, because it occurs in both wild-type and Mdm2(-/-) cells. SiRNA-mediated reduction in the levels of beta-TrCP1 and other members of the SCF(beta-TrCP1)E3 ubiquitin ligase complex or overexpression of a dominant negative form of beta-TrCP1 enhances p53 stability. Substitutions at Ser-362 and 366 of p53 by alanines (p53 AA) result in reduced phosphorylation of p53 by IKK2, decreased association with beta-TrCP1, and thus increased stability of p53 and expression of p53 target genes such as p21, altering the G1 phase of the cell cycle. Our results identify IKK2 and beta-TrCP1 as novel regulators of the p53 pathway and suggest that blocking of IKK2 and beta-TrCP1 could be a means of regulating p53 stability and thereby modulating its biological activity.

PMID: 19196987 [PubMed - indexed

Cancer Lett. 2008 Sep 8;268(1):137-45. Epub 2008 May 22.

A novel domain of BRCA1 interacts with p53 in breast cancer cells.

Buck M.

Department of Medicine, Veterans Healthcare Medical Center, San Diego, CA 92161, USA. mbuck@ucsd.edu

Abstract

The interactions between BRCA1 and p53 are relevant for understanding hereditary breast and ovarian cancer. Although in vitro studies reported that BRCA1 (amino acids 224-500) and the second BRCT domain of the BRCA1 C-terminus may interact with p53, quantitative biophysical measurements indicate that these regions of BRCA1 do not bind efficiently to p53. Here we show that BRCA1 interacts with p53 in vivo in breast cancer cells, through another BRCA1 domain (amino acids 772-1292). Expression of a truncated BRCA1 (amino acids 772-1292) stimulated p53 DNA-binding and transcription activities and apoptosis, recapitulating some effects of DNA damage. These results suggest that a novel domain of BRCA1 may interact with p53 in breast cancer cells.

PMID: 18501503 [PubMed - indexed for MEDLINE]