Nuclear localization signal of ING4 plays a key role in its binding to p53

ING4, a novel member of ING family, is recently reported to interact with tumor suppressor p53 and negatively regulate the cell growth with significant G2/M arrest of cell cycle in HepG2 cells through upregulation of p53-inducible gene p21. However, which region of ING4 could have contributed to the binding to p53 remains largely unclear. Herein, the GST-pulldown experiments revealed that the middle region of ING4, a potential bipartite nuclear localization signal (NLS), could be involved in the binding to p53. Furthermore, the interaction of ING4 to p53 was abrogated in vitro and in vivo when certain mutations or the entire deletion of the NLS domain occurred. More interestingly, the mutations of the NLS domain could alter the ING4 nuclear localization, disrupt the interaction of ING4 with p53, and even, deregulate the p53-inducible gene p21 in MCF-7 cells. All data indicated that the NLS domain of ING4 is essential for the binding of ING4 to p53 and the function of ING4 associated with p53.     

Subcellular localization of HCV core protein regulates its ability for p53 activation and p21 suppression

An internal RNA standard proved less suitable in bacterial gene expression experiments. We therefore developed a method for simultaneous RNA and gDNA (genomic DNA) isolation from in vitro and in vivo samples containing staphylococci and combined it with quantitative PCR. The reliability of gDNA for bacterial quantification and for standardisation in gene expression experiments was evaluated. Quantitative PCR proves equivalent to quantitative culture for in vitro samples, and superior for in vivo samples. In gene expression experiments, gDNA permits a good standardisation for the initial amount of bacteria. The average interassay variability of the in vitro expression is 20.1%. The in vivo intersample variability was 73.3%. This higher variability can be attributed to the biological variation of gene expression in vivo. This method permits exact quantification of the number of bacteria and the expression of genes in staphylococci in vivo (e.g., in biofilms, evolution in time) and in vitro.     

A high-content chemical screen identifies ellipticine as a modulator of p53 nuclear localization

p53 regulates apoptosis and the cell cycle through actions in the nucleus and cytoplasm. Altering the subcellular localization of p53 can alter its biological function. Therefore, small molecules that change the localization of p53 would be useful chemical probes to understand the influence of subcellular localization on the function of p53. To identify such molecules, a high-content screen for compounds that increased the localization of p53 to the nucleus or cytoplasm was developed, automated, and conducted. With this image-based assay, we identified ellipticine that increased the nuclear localization of GFP-mutant p53 protein but not GFP alone in Saos-2 osteosarcoma cells. In addition, ellipticine increased the nuclear localization of endogenous p53 in HCT116 colon cancer cells with a resultant increase in the transactivation of the p21 promoter. Increased nuclear p53 after ellipticine treatment was not associated with an increase in DNA double stranded breaks, indicating that ellipticine shifts p53 to the nucleus through a mechanism independent of DNA damage. Thus, a chemical biology approach has identified a molecule that shifts the localization of p53 and enhances its nuclear activity. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. G. Wei Xu and Imtiaz A. Mawji have contributed equally to this work.     

SW480, a p53 double-mutant cell line retains proficiency for some p53 functions

During certain types of cellular stress, the p53 tumor suppressor protein binds to DNA and transactivates a variety of genes that regulate critical responses including apoptosis, cell cycle checkpoints, differentiation, and angiogenesis. In addition, functional p53 is known to be required for efficient nucleotide excision repair (NER) of bulky DNA adducts generated through exposure to environmental mutagens such as UV light. Nonetheless, we previously showed that the model p53-mutated human adenocarcinoma strain SW480 is proficient in the removal of UV-induced cyclobutane pyrimidine dimers (CPD) via NER. We undertook the present study to begin probing the molecular basis for this unexpected repair phenotype. Cytogenetic analysis indicated that SW480 is stable at the chromosomal level, i.e. manifests a karyotypic profile very similar to that revealed for this line as far back as 14 years ago. After fluorescence in situ hybridization (FISH), using a probe complementary to the p53 gene, we found that 98% of the SW480 interphase nuclei contains three copies of the gene, later revealed to be localized on intact short arms of three chromosomes 17. DNA sequence analysis further showed that all three p53 copies in SW480 carry two point mutations (R273H and P309S), and levels of the corresponding mutated p53 protein are about 20-fold higher than in the closely related p53 wild-type strain LoVo. Using an electrophoretic mobility shift assay (EMSA), we demonstrated that R273H/P309S p53 is able to bind with wild-type affinity to its consensus DNA sequence in vitro. Analysis of p21(Cip1/WAF1) expression and in vivo footprinting by ligation-mediated PCR (LMPCR) showed that, in wild-type LoVo cells, an exposure to cellular stress (e.g. UV or ionizing radiation) is necessary for p53 activation of the p21(Cip1/WAF1) promoter. In contrast, the R273H/P309S-mutated p53 protein in SW480 constitutively activates p21(Cip1/WAF1) in the absence of stress through an unknown mechanism. A similar phenomenon whereby mutated p53 in SW480 is able to induce NER-related proteins might explain the normal DNA repair phenotype previously observed in this strain. For now we conclude that, in general, results obtained using SW480 as a p53-deficient cell line should be interpreted very cautiously.     

A prognostic signature of defective p53-dependent G1 checkpoint function in melanoma cell lines

Melanoma cell lines and normal human melanocytes (NHM) were assayed for p53-dependent G1 checkpoint response to ionizing radiation (IR)-induced DNA damage. Sixty-six percent of melanoma cell lines displayed a defective G1 checkpoint. Checkpoint function was correlated with sensitivity to IR with checkpoint-defective lines being radio-resistant. Microarray analysis identified 316 probes whose expression was correlated with G1 checkpoint function in melanoma lines (P≤0.007) including p53 transactivation targets CDKN1A, DDB2, and RRM2B. The 316 probe list predicted G1 checkpoint function of the melanoma lines with 86% accuracy using a binary analysis and 91% accuracy using a continuous analysis. When applied to microarray data from primary melanomas, the 316 probe list was prognostic of 4-yr distant metastasis-free survival. Thus, p53 function, radio-sensitivity, and metastatic spread may be estimated in melanomas from a signature of gene expression.     

Curcumin induced apoptosis is mediated through oxidative stress in mutated p53 and wild type p53 colon adenocarcinoma cell lines

Curcumin has anti‐oxidant, anti‐cancer and anti‐carcinogen property. Our laboratory had previously reported that, curcumin treatment induces reactive oxygen species (ROS) generation in HT‐29 cell line, an effect contradictory to its anti‐oxidant property. This study evaluates the role of p53 in curcumin mediated ROS generation and cell death. Curcumin induced ROS was determined by 2’,7’‐dichlorofluorescein and apoptosis by Hoechst33342/PI staining in HT‐29 and HCT‐116 cell lines. ROS generation occurs within 1 hour of 40 µM curcumin treatment and a reduction was observed by third hour in HCT‐116 insinuating p53 involvement. N‐acetyl cysteine (NAC) pre‐treatment effectively quenched ROS and inhibited membrane potential loss in HT‐29, but less effective in HCT‐116. Mitochondrial membrane potential loss is evident with 10 and 40 µM curcumin in HCT‐116 and at 40 µM curcumin in HT‐29. Total p53 protein level increase was observed by 24 hours in HCT‐116 upon NAC pre‐treatment. Our results indicate that curcumin induces ROS mediated cell death in colon adenocarcinoma cell lines and may be mediated via p53.     

p53家族及其通路相关蛋白调节母性生殖的新功能

p53是一种重要的抗癌基因,同时它也是机体感受环境压力并进行相应调节的关键基因之一。最近的研究发现东亚人群p53 Arg72Pro受到冬季温度自然选择,表明p53可能在生殖中发挥作用。同时,p53及其通路中的癌基因鼠双微体2(Murinedoubleminute2,Mdm2)、MdmX和Hausp(Herpesvirus-associated ubiquitin-specific protease)基因的单核苷酸多态性(Single nucleotide polymorphisms,SNP)与女性生殖疾病易感性相关。P53蛋白通过其DNA结合区(DNA-binding domain,DBD)调控白血病抑制因子(Leukaemiainhibitory factor,LIF)表达,从而影响胚胎植入过程,实现其在母性生殖中的作用。p53通路中Mdm2、MdmX和Hausp可以调控P53蛋白的表达水平和活性,同时还可以在胚胎植入时准确的调控p53的表达水平,促进胚胎植入;P53家族成员P63、P73具有P53相似的DBD区,但P63和P73是通过别的途径影响到母性生殖;在卵母细胞受到射线或者化学损伤后,P63能促进其凋亡,减少畸型的产生;P73能影响纺锤体复合物的组装,而纺锤体复合物缺失将导致胚泡质量低下,微管结合的动粒缺失和细胞非整倍性的增加。文章主要综述了p53家族、p53通路中的相关蛋白对母性生殖的影响,为提高IVF-ET成功指出了新方法,同时也为不明原因的不孕患者提供了新的诊断思路,将有助于制定合理的个性化治疗不孕方案。     

Establishment and characterization of a human cell line derived from a uterine papillary serous carcinoma with wild-type p53 function

Uterine papillary serous carcinoma is an uncommon histologic subtype of endometrial cancer that behaves aggressively and has a poor prognosis. We successfully established a uterine papillary serous carcinoma cell line. The population-doubling time was approximately 16 h. Although loss of p53 function is considered critical for the molecular pathogenesis of uterine papillary serous carcinoma, p53 was not only mutated but functionally active in this cell line. This newly established cell line should be useful for investigating the characteristics of uterine papillary serous carcinoma.     

转化的大鼠胚胎成纤维细胞系与p53val135功能关系的研究

A1-5是一株典型的温度敏感的p53^val135细胞系,许多实验室用它来研究p53的功能,我们首次报道了A1-5细胞表现出非常强的抗辐射性并伴随不同寻常强的G2延迟效应,B4是另一株温度敏感的p53^val135细胞系,A1-5与B4细胞都 是来源于同样的原代转化的大鼠胚胎成纤维细胞系,只是来自不同的转染实验,本阐明了A1-5细胞非常强的抗辐射性及不同寻常强的G2停滞效应与p53val135的功能无关,A1-5细胞系具有的特殊表型是研究放射敏感性新性质的独特的模型。     

Expression of the p53 Gene and Activation of p53-Dependent Transcription in Melanoma Cell Lines

Malignant melanoma has poor prognosis because of its high metastatic potential and resistance to chemotherapy. A possible approach to more effective therapy is induction of p53-dependent apoptosis. This approach is promising, since the wild-type _p53 is expressed in most melanomas. An attempt was made to estimate the functional activity of p53 in several malignant melanoma cell lines. Most lines were characterized by a high protein level and nuclear localization of p53. All cell lines expressing the wild-type p53 showed stabilization of p53, its translocation into the nucleus, and activation of several target genes in response to DNA-damaging agents, suggesting that p53 was functionally active. A high-molecular-weight protein localized in the cytoplasm and mimicking a p53 epitope was found in several cell lines. It was shown that the DO-1 epitope is not derived from p53, ruling out cytoplasmic retention of p53 in melanoma cell lines. A mechanism of camptothecin-induced stabilization of p53 by decreasing the level of the HDM2 mRNA was described for melanoma cells but not for normal melanocytes, suggesting a differential effect of camptothecin on tumor-derived and primary cells.__________Translated from Molekulyarnaya Biologiya, Vol. 39, No. 3, 2005, pp. 445–456.Original Russian Text Copyright © 2005 by Razorenova, Agapova, Chumakov.     

UV-induced interaction between p38 MAPK and p53 serves as a molecular switch in determining cell fate

p53 plays a fundamental role in the maintenance of genome integrity after DNA damage, deciding whether cells repair and live, or die. However, the rules that govern its choice are largely undiscovered. Here we show that the functional relationship between p38 and p53 is crucial in defining the cell fate after DNA damage. Upon low dose ultraviolet (UV) radiation, p38 and p53 protect the cells from apoptosis separately. Conversely, they function together to favor apoptosis upon high dose UV exposure. Taken together, a UV-induced, dose-dependent interaction between p38 and p53 acts as a switch to determine cell fate.

Structured summary

MINT-8050838: p53 (uniprotkb:P02340) physically interacts (MI:0915) with p38 (uniprotkb:P47811) by anti bait coimmunoprecipitation (MI:0006)MINT-8050948: p53 (uniprotkb:P04637) physically interacts (MI:0915) with p38 (uniprotkb:P47811) by anti tag coimmunoprecipitation (MI:0007)     

Analysis of the p53 gene alterations in mouse embryo fibroblast cell line Balb 3T12 and its derivative 312

We have analysed the status of the p53 gene in the mouse embryo fibroblast cell line Balb 3T12 (TD₅₀=10⁶) and its transformed clonal derivative 312 (TD₅₀=10⁴) with an aim to determine whether there exists a correlation between increased tumorigenicity and clonal expansion of cells bearing a mutation in the p53 gene. While Southern hybridizations did not show any obvious changes in the p53 gene organization in 3T12 and 312 cells, sequencing the p53 cDNA revealed that 3T12 is mutated at the amino acid residue 233 (Tyr→ Asp) whereas 312 is mutated at the residue 132 (Cys→Trp). Exploiting the altered RFLP pattern due to mutations, we identified that 3T12 contains p53 alleles that are different from the already identified mutant p53. On the basis of these observations, we conclude that 3T12 and 312 have evolved independently.     

Binding sequence-dependent regulation of the human proliferating cell nuclear antigen promoter by p53

Exposure of a lung epithelial cell line to ionizing radiation (IR) arrests cell cycle progression through 48 h post-exposure. Coincidentally, IR differentially activates expression of the cell cycle inhibitor, p21/WAF1, and the DNA replication protein, proliferating cell nuclear antigen (PCNA). p21/WAF1 mRNA levels remain elevated through 48 h post-exposure to IR, while PCNA mRNA levels increase transiently at early times. Since p21/WAF1 inhibits DNA replication by directly binding PCNA, the relative levels of the two proteins can determine cell cycle progression. The PCNA p53-binding site displayed reduced p53 binding affinity in vitro relative to the distal p21/WAF1 p53-binding site. Substitution of the p21/WAF1 site for the resident p53-binding site in the PCNA promoter altered the responses to increasing amounts of p53 or IR in transient expression assays. The p21/WAF1 p53-binding site sustained activation of the chimeric PCNA promoter under conditions (high p53 levels or high dose IR) that the PCNA p53-binding site did not. Binding site-specific regulation by wild-type p53 was not observed with mutant p53 harboring a serine to alanine change at amino acid 46. Limited activation of the PCNA promoter by p53 and its modified forms would restrict the amount of PCNA made available for DNA repair.     

Functional characterization of a new p53 mutant generated by homozygous deletion in a neuroblastoma cell line

p53 is a key modulator of a variety of cellular stresses. In human neuroblastomas, p53 is rarely mutated and aberrantly expressed in cytoplasm. In this study, we have identified a novel p53 mutant lacking its COOH-terminal region in neuroblastoma SK-N-AS cells. p53 accumulated in response to cisplatin (CDDP) and thereby promoting apoptosis in neuroblastoma SH-SY5Y cells bearing wild-type p53, whereas SK-N-AS cells did not undergo apoptosis. We found another p53 (p53DeltaC) lacking a part of oligomerization domain and nuclear localization signals in SK-N-AS cells. p53DeltaC was expressed largely in cytoplasm and lost the transactivation function. Furthermore, a 3'-part of the p53 locus was homozygously deleted in SK-N-AS cells. Thus, our present findings suggest that p53 plays an important role in the DNA-damage response in certain neuroblastoma cells and it seems to be important to search for p53 mutations outside DNA-binding domain.