UNIPROT:P04637 - FACTA Search

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Query: UNIPROT:P04637 (p53)
77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Breast tumor suppressor gene 1 (BRCA1) plays an essential role in maintaining genomic integrity. Here we show that mouse Brca1 is required for DNA-damage repair and crossing-over during spermatogenesis. Male Brca1(Delta11/Delta11)p53(+/-) mice that carried a homozygous deletion of Brca1 exon 11 and a p53 heterozygous mutation had significantly reduced testicular size and no spermatozoa in their seminiferous tubules. During spermatogenesis, homologous chromosomes from the mutant mice synapsed and advanced to the pachytene stage but failed to progress to the diplotene stage. Our analyses revealed that the Brca1 mutation affected cellular localization of several DNA damage-repair proteins. This included prolonged association of gammaH2AX with sites of DNA damage, reduced sex body formation, diminished Rad51 foci and absence of Mlh1 foci in the pachytene stage. Consequently, chromosomes from mutant mice did not form chiasmata, a point that connects exchanging homologous chromosomes. Brca1-mutant spermatocytes also exhibited decreased RNA expression levels of several genes that are involved in DNA-damage repair, including RuvB-like DNA helicase, XPB, p62 and TFIID. Of note, the premature termination of spermatogenesis at the pachytene stage was accompanied by increased apoptosis by both p53-dependent and p53-independent mechanisms. Thus, our study revealed an essential role of Brca1 in DNA-damage repair and crossing-over of homologous chromosomes during spermatogenesis.
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PMID:Impaired meiotic DNA-damage repair and lack of crossing-over during spermatogenesis in BRCA1 full-length isoform deficient mice. 1264 2

Functional tumor suppressor p53 is mainly required for efficient global genomic repair (GGR), a subpathway of nucleotide excisions repair (NER). In this study, the regulatory effect of p53, on the spaciotemporal recruitment of XPC and TFIIH to DNA damage sites, was investigated in repair-proficient and -deficient human cells in situ. Photoproducts were induced through micropore UV irradiation of discrete subnuclear areas of intact cells and the specific lesions, as well as recruited repair factors, were detected by immunofluorescent intensity and density of the damaged DNA subnuclear spots (SNS). Both cyclobutane pyrimidine dimers (CPD) and 6-4 photoproducts (6-4PP) were visualized in situ at SNS within irradiated nuclear foci. The in situ repair kinetics revealed that p53-WT normal fibroblasts are proficient for the repair of both CPD and 6-4PP, whereas, p53-Null Li-Fraumeni syndrome (LFS) fibroblasts fail to efficiently repair CPD but not 6-4PP. Colocalization experiments of the NER factors showed that in normal human cells, XPC and TFIIH are rapidly and efficiently recruited to DNA damage within SNS. By contrast, recruitment of both XPC and TFIIH to DNA damage in SNS occurred much less efficiently in p53-Null or p53-compromised cells. The total cellular levels of XPC and XPB were similar in both p53-WT and -Null cells and remained unchanged up to 24h following UV irradiation. The results also showed that dispersal of recruited XPC and TFIIH from DNA damage SNS occurs within a short period after DNA damage. Such dispersal requires functional XPA, XPF and XPG proteins. Taken together, the results demonstrated that p53 plays a pronounced role in the damage recognition and subsequent assembly of repair machinery during GGR and the recruitment of XPC and TFIIH to CPD is p53-dependent. Most likely mechanism of this p53 action is through its downstream effector protein, DDB2.
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PMID:Tumor suppressor p53 dependent recruitment of nucleotide excision repair factors XPC and TFIIH to DNA damage. 1271 9

Xeroderma pigmentosum (XP), Cockayne syndrome (CS) and trichothiodystrophy (TTD) are genetic disorders with very different clinical features, but all associated with defects in nucleotide excision repair. Defects in the XPA or XPC genes confer sensitivity to UV carcinogenesis in both humans and mice, but only XPA(-/-) mice have increased acute responses to UV exposure, whereas XPC(-/-) mice are normal in this respect. Both XPE and XPF proteins have functions separate from their role in NER, but the exact nature of these functions has not yet been established. The CSA and CSB genes responsible for CS are both components of complexes associated with RNA polymerase II and their role is thought to be in assisting polII in dealing with transcription blocks. XPB and XPD proteins are components of transcription factor TFIIH, which is involved in both basal and activated transcription. XPB is part of the core of TFIIH and has a central role in transcription, whereas XPD connects the core to the CAK subcomplex, and can tolerate many different mutations. Subtle differences in the effects of these different mutations on the many activities of TFIIH and on its stability determine the clinical outcomes, which can be XP, TTD, XP with CS, XP with TTD or COFS. Features of single and double mutant mice indicate that the neurological and ageing features associated with these disorders result from the defects in NER in association with the transcriptional deficiencies. Skin tumours in XP patients have mutations characteristic of UV-induction in the ras, p53 and ptch genes, showing that sunlight-induced mutations in these genes are important in carcinogenesis in XP patients.
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PMID:DNA repair-deficient diseases, xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy. 1472 16

The current studies represent the first step in assessing the utility of harringtonine in combination with cisplatin as an improved approach for treating ovarian cancer. Three ovarian cancer cell lines, platinum-sensitive A2780, and platinum-resistant A2780/CP70 and OvCar-3, were exposed to their respective IC(50) dose of cisplatin for 1 h with or without a 24-h pretreatment with harringtonine. The level of platinum-DNA adducts was determined by atomic absorption spectrometry (AAS). These studies show for the first time that harringtonine pretreatment significantly increased the amount of platinum-DNA adducts in all ovarian cancer cell lines by 2-4 fold, immediately following 1-h exposure to cisplatin. Moreover, the level of cisplatin-DNA adducts in harringtonine-pretreated cells remained elevated by 3-4.7-fold for at least 6 h after cisplatin was removed, relative to cells only exposed to cisplatin. In all three cell lines the removal (repair) of platinum-DNA adducts was not significantly altered by harringtonine. In addition, the extent to which harringtonine altered the expression of select DNA damage response genes (p53, P16, ERCC1 and XPB) was determined using RT-PCR and Southern hybridization in A2780 and A2780/CP70 cells. The expression of ERCC1 and XPB RNAs were only modestly altered by harringtonine, consistent with a lack of effect of harringtonine on repair of cisplatin-DNA damage. However, harringtonine altered expression of p53 and P16 RNAs in both cell lines, although the down-regulation of p53 and P16 RNAs by harringtonine were more pronounced in A2780 cells. The novel observation that harringtonine augments platinum-DNA adducts in both platinum-sensitive and -resistant ovarian cancer cells indicates this combination of drugs may have utility in treating ovarian cancer and may be especially useful in managing platinum-resistant cancers. Additional studies are required to determine which sequence of these drugs is most beneficial, as well as the mechanism by which harringtonine increases cisplatin-DNA damage in ovarian cancer cells.
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PMID:Combinatorial treatment of ovarian cancer cells with harringtonine and cisplatin results in increased cisplatin-DNA adducts. 1501 Aug 81

Splenic marginal zone lymphoma (SMZL) is a lymphoma type of putative marginal zone B-cell origin. No specific genetic alterations have yet been demonstrated in SMZL. Clinically, SMZL is a low-grade B-cell non-Hodgkin lymphoma. However, the presence of p53 mutation, 7q22-7q32 deletion or the absence of somatic hypermutations of immunoglobulin genes has been correlated with a worse prognosis. In this study, we analyzed genome-wide gene expression of 24 cases of SMZL using the microarray technique. The AP-1 transcription factors c-jun, junD, junB, and c-fos as well as Notch2 were found to be specifically up-regulated. These data were confirmed by real-time PCR and immunohistochemical staining of tissue sections. The absence of concordant high expression of the MAP kinases, the signaling cascade leading to AP-1 up-regulation, suggests autoregulation of the AP-1 transcription factors and an important role in SMZL oncogenesis. High expression of Notch2, a transcription factor that induces marginal zone B-cell differentiation, is highly suggestive for a marginal zone B-cell origin of SMZL. In addition, SMZL with the 7q deletion showed high expression of TGF-beta1 and low expression of the DNA helicase XPB, a crucial part of the nucleotide excision repair complex, possibly explaining the more aggressive clinical course of those cases.
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PMID:Constitutive expression of the AP-1 transcription factors c-jun, junD, junB, and c-fos and the marginal zone B-cell transcription factor Notch2 in splenic marginal zone lymphoma. 1550 68

The severe xeroderma pigmentosum/Cockayne syndrome (XP/CS) syndrome is caused by mutations in the XPB, XPD and XPG genes that encode the helicase subunits of TFIIH and the 3' endonuclease of nucleotide excision repair (NER). Because XPB and XPD have been implicated in p53-mediated apoptosis, we examined the possible involvement of XPG in this process. After ultraviolet light (UV) irradiation, primary fibroblasts of XP complementation group G (XP-G) individuals with CS enter apoptosis more readily than other NER-deficient cells, but this is unlinked to unrepaired damage. These XP-G/CS cells accumulate p53 post-UV but they fail to accumulate the 90/92 kDa isoforms of Mdm2 and their cellular distribution of Mdm2 is impaired. Apoptosis levels revert to wild type, Mdm2 90/92 kDa isoforms accumulate, and Mdm2 regains its normal post-UV nuclear location in transduced XP-G/CS cells expressing wild-type XPG, but not an XPG catalytic site mutant. These results suggest that XPG suppresses UV-induced apoptosis and that this suppression, most simply, requires its endonuclease function.
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PMID:Suppression of UV-induced apoptosis by the human DNA repair protein XPG. 1616 68

A subset of DNA helicases, the RecQ family, has been found to be associated with the p53-mediated apoptotic pathway and is involved in maintaining genomic integrity. This family contains the BLM and WRN helicases, in which germline mutations are responsible for Bloom and Werner syndromes, respectively. TFIIH DNA helicases, XPB and XPD, are also components in this apoptotic pathway. We hypothesized that there may be some redundancy between helicases in their ability to complement the attenuated p53-mediated apoptotic levels seen in cells from individuals with diseases associated with these defective helicase genes. The attenuated apoptotic phenotype in Bloom syndrome cells was rescued not only by ectopic expression of BLM, but also by WRN or XPB, both 3' --> 5' helicases, but not expression of the 5' --> 3' helicase XPD. Overexpression of Sgs1, a WRN/BLM yeast homolog, corrected the reduction in BS cells only, which is consistent with Sgs1 being evolutionarily most homologous to BLM. A restoration of apoptotic levels in cells from WS, XPB or XPD patients was attained only by overexpression of the specific helicase. Our data suggest a limited redundancy in the pathways of these RecQ helicases in p53-induced apoptosis.
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PMID:Redundancy of DNA helicases in p53-mediated apoptosis. 1628 11

Eukaryotic cells respond to a variety of DNA insults by triggering a common signal transduction cascade, known as checkpoint response, which temporarily halts cell-cycle progression. Although the main players involved in the cascade have been identified, there is still uncertainty about the nature of the structures that activate these surveillance mechanisms. To understand the role of nucleotide excision repair (NER) in checkpoint activation, we analyzed the UV-induced phosphorylation of the key checkpoint proteins Chk1 and p53, in primary fibroblasts from patients with xeroderma pigmentosum (XP), Cockayne syndrome (CS), trichothiodystrophy (TTD), or UV light-sensitive syndrome. These disorders are due to defects in transcription-coupled NER (TC-NER) and/or global genome NER (GG-NER), the NER subpathways repairing the transcribed strand of active genes or the rest of the genome, respectively. We show here that in G0/G1 and G2/M phases of the cell cycle, triggering of the DNA damage cascade requires recognition and processing of the lesions by the GG-NER. Loss of TC-NER does not affect checkpoint activation. Mutations in XPD, XPB, and in TTDA, encoding subunits of the TFIIH complex, involved in both transcription and NER, impair checkpoint triggering. The only exception is represented by mutations in XPD, resulting in combined features of XP and CS (XP/CS) that lead to activation of the checkpoint cascade after UV radiation. Inhibition of RNA polymerase II transcription significantly reduces the phosphorylation of key checkpoint factors in XP/CS fibroblasts on exposure to UV damage.
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PMID:DNA nucleotide excision repair-dependent signaling to checkpoint activation. 1708 60

The tumor suppressor p53 enhances repair of UVC-induced DNA damage. The comet-NE assay, a conventional alkaline comet assay which includes a nuclear digestion step, was used to examine the effects of p53 on the excision activity of nuclear extracts (NEs). In contrast with untreated NEs, NEs immunodepleted of p53 or NEs of p53-null cells were unable to excise UVC-induced DNA adducts. Introduction of p53 by transfection restored the excision activity to NEs of p53-null cells. Deletion of the N-terminal 99 amino acids and/or the C-terminal 85 amino acids of p53 barely affected the excision activity, whereas further deletion of the C-terminus of p53 by another 10 amino acids completely abolished the excision activity of NEs. Immunostaining following localized UV irradiation was used to examine the effects of p53 on the recruitment of repair proteins for nucleotide excision repair (NER). Although recruitment of XPC occurred regardless of the presence of p53, the recruitment of XPB was p53-dependent. However, p53 with the 95 amino acid deletion at its C-terminus was unable to support this recruitment of XPB. Consistently, intact p53 (but not the C-terminal 95 residue truncated version) was detected in co-immunoprecipitation assays with an anti-XPB antibody. These results support the hypothesis that p53 facilitates NER through direct involvement by protein-protein interactions.
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PMID:Direct involvement of the tumor suppressor p53 in nucleotide excision repair. 1834 5

The cytosine nucleoside analogue 2'-C-cyano-2'-deoxy-1-beta-d-arabino-pentofuranosylcytosine (CNDAC) causes DNA single-strand breaks after its incorporation into DNA. This investigation sought to determine if DNA excision repair pathways were activated to repair this damage. Neither the base excision repair nor the mismatch repair pathway seemed to be involved. Cells deficient in the CSB protein, which initiates transcription-coupled nucleotide excision repair (NER) pathway (TC-NER), exhibited increased clonogenic sensitivity to CNDAC, whereas cells deficient in XPC, which initiates global genome NER, were slightly resistant relative to wild-type cells. The cells lacking either helicase XPB, which unwinds 5' of the lesion, or endonuclease XPF, which incises 5' to a lesion, exhibited increased clonogenic sensitivity to CNDAC, as did cells lacking the XPF partner protein ERCC1. This sensitization was independent of p53 function. Repletion of XPF restored sensitivity comparable with the wild type. In contrast, cells lacking either XPD, the 3'-helicase, or the 3'-endonuclease XPG were equally as sensitive as wild-type cells. In comparison, cells deficient in XPF were not sensitized to other cytosine nucleoside analogues, troxacitabine and cytarabine. Thus, the single-strand nick caused by CNDAC is recognized and, in part, repaired by the TC-NER pathway. NER proteins that function in the 5' direction relative to the UV-induced lesion also participate in the repair of the CNDAC-induced nick, in contrast to proteins that process on the 3' side of the lesion.
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PMID:Repair of 2'-C-cyano-2'-deoxy-1-beta-D-arabino-pentofuranosylcytosine-induced DNA single-strand breaks by transcription-coupled nucleotide excision repair. 1848 73

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