Correlation of appearance of metastasis-associated protein1 (Mta1) with spermatogenesis in developing mouse testis

Mta1, a representative of the MTA gene family, is believed to be involved in the metastasis of malignant tumors. However, a systematic study of its physiological function has not been performed. It has been found in normal mouse organs at relatively low levels, except for in testis, suggesting a potential function in the male reproductive system. In order to explore the role of Mta1 protein during spermatogenesis, its expression in adult mouse testis was compared with that in developing mouse testis and in testis from adult mice treated with methoxyacetic acid, which selectively depletes primary spermatocytes. Quantitative analysis revealed that Mta1 protein gradually increased in the testis from 14 days postnatally. Immunolocalization analysis demonstrated strong signals in the seminiferous tubules, and Mta1 was predominantly present in the nucleus of primary spermatocytes and spermatogonia from 14 days postnatally. The most intensive staining was located in the nucleus of pachytene spermatocytes in mature testes. The expression pattern of Mta1 during spermatogenesis was also shown to be stage-specific by immunohistochemistry analysis. Finally, dramatic loss of Mta1 expression from pachytene spermatocytes was observed in the spermatogenic-arrested adult mouse testis. These results collectively demonstrate that Mta1 appears during postnatal testis development and suggest that this expression may be crucial for spermatogenesis. This study was supported by the Natural Science Foundation of China (2006: 30570982; 2003: 30370750; 2003: 30371584).     

Multifaceted functions of Siva-1: more than an Indian God of Destruction

Siva-1, as a p53-inducible gene, has been shown to induce extensive apoptosis in a number of different cell lines. Recent evidence suggests that Siva-1 functions as a part of the auto-regulatory feedback loop that restrains p53 through facilitating Mdm2-mediated p53 degradation. Also, Siva-1 plays an important role in suppressing tumor metastasis. Here we review the current understanding of Siva-1-mediated apoptotic signaling pathway. We also add comments on the p53-Siva-1 feedback loop, the novel function of Siva-1 in suppressing tumor metastasis, and their potential implications.     

Multiple domains of the mouse p19ARF tumor suppressor are involved in p53-independent apoptosis

The ARF (p19ARF for the mouse ARF consisting of 169 amino acids and p14ARF for the human ARF consisting of 132 amino acids) genes upregulate p53 activities to induce cell cycle arrest and sensitize cells to apoptosis by inhibiting Mdm2 activity. p53-independent apoptosis also is induced by ectopic expression of p19ARF. We constructed various deletion mutants of p19ARF with a cre/loxP-regulated adenoviral vector to determine the regions of p19ARF which are responsible for p53-independent apoptosis. Ectopic expression of the C-terminal region (named C40) of p19ARF whose primary sequence is unique to the rodent ARF induced prominent apoptosis in p53-deficient mouse embryo fibroblasts. Relatively low-grade but significant apoptosis also was induced in p53-deficient mouse embryo fibroblasts by ectopic expression of p19ARF1-129, a p19ARF deletion mutant deficient in the C40 region. In contrast, ectopic expression of the wild-type p14ARF did not induce significant apoptosis in human cells. Taken together, we concluded that p53-independent apoptosis was mediated through multiple regions of the mouse ARF including C40, and the ability of the ARF gene to mediate p53-independent apoptosis has been not well conserved during mammalian evolution.     

促凋亡基因p53AIP1的研究进展

p53AIPl基因是近年发现的促凋亡基因,在p53依赖性的凋亡通路中起重要作用。p53AIPl介导线粒体凋亡途径,其表达依赖于p53蛋白的Ser^46的磷酸化。p53AIPl可直接促进凋亡,其促凋亡作用可能强于p53本身,并对p53抗性的肿瘤细胞也有作用。因此,对p53AIPl的深入研究可能会为对p53基因治疗有抗性的肿瘤患者带来新的希望。     

DNA损伤诱导的长链非编码RNA-UCA1促进HeLa细胞增殖

尿路上皮癌抗原1 (UCA1)是一种长链非编码RNA,在多种肿瘤内高表达.然而,其在宫颈癌细胞和组织中的表达报告颇不一致,且功能尚未确定.本文探索UCA1在宫颈癌HeLa细胞中的生物学功能.实时定量PCR（qRT-PCR）结果显示,UCA1、p21和p53 mRNA在阿霉素（doxorubicin,DOX）或γ射线照射的HeLa细胞中表达上调|相反,敲减p53表达则可抑制DOX诱导的UCA1上调.表明DNA损伤诱导的UCA1可能与p53有关.转染结合CCK8检测HeLa细胞增殖活力结果显示,与对照比较,过表达UCA1促进HeLa细胞增殖,干扰UCA1表达则减缓细胞增殖.此外,流式细胞术结果显示,过表达UCA1导致阿霉素诱导的凋亡率下降;siRNA抑制UCA1表达后引起细胞G2/M期比例上升,S期下降,且阿霉素诱导的细胞凋亡率上升.上述结果说明,DNA损伤诱导的UCA1可促进HeLa细胞增殖,减少细胞凋亡.然而,是否DNA损伤诱导的UCA1上调依赖p53尚需进一步实验证明.     

p19ARF-induced p53-independent apoptosis largely occurs through BAX

Combined disruption of the ARF gene and the p53 gene causes mouse predisposition to tumors of a wider variety and at a higher frequency than disruption of the p53 gene, indicating that the ARF gene has p53-independent anti-tumor function in addition to p53-dependent function. Coincidentally with this notion, ectopic expression of the p19(ARF) induces apoptosis for wild-type mouse embryo fibroblasts which have been immortalized by introduction of the SV40 virus genome (SV40-MEFs). The protein expression levels of p53, p21(Cip1), and Bax were not upregulated by ectopic expression of p19(ARF) in SV40-MEFs, indicating that expression of p19(ARF) induced apoptosis through p53-independent pathways in this system. Ectopic expression of p19(ARF) induced prominent apoptosis even in SV40-Bak-/-MEFs. In contrast, expression of p19(ARF) induced only a very low grade of apoptosis in Bax-/- or Bax-/-/Bak-/-SV40-MEFs. Remarkable attenuation of p19(ARF)-induced apoptosis by disruption of the Bax gene thus leads to the conclusion that Bax plays a major role in p53-independent apoptosis induced by p19(ARF).     

p53DINP1, a p53-inducible gene, regulates p53-dependent apoptosis

Using the differential display method combined with a cell line that carries a well-controlled expression system for wild-type p53, we isolated a p53-inducible gene, termed p53DINP1 (p53-dependent damage-inducible nuclear protein 1). Cell death induced by DNA double-strand breaks (DSBs), as well as Ser46 phosphorylation of p53 and induction of p53AIP1, were blocked when we inhibited expression of p53DINP1 by means of an antisense oligonucleotide. Overexpression of p53DINP1 and DNA damage by DSBs synergistically enhanced Ser46 phosphorylation of p53, induction of p53AIP1 expression, and apoptotic cell death. Furthermore, the protein complex interacting with p53DINP1 was shown to phosphorylate Ser46 of p53. Our results suggest that p53DINP1 may regulate p53-dependent apoptosis through phosphorylation of p53 at Ser46, serving as a cofactor for the putative p53-Ser46 kinase.     

抑癌基因HLJ1与肿瘤的演进

HLJ1基因是一新发现的抑癌基因,属于Dnaj类HSP40家族,其与肿瘤的复发、转移密切相关。文章着重介绍了HLJ1通过上调STAT1、p21WAF1的表达及下调CyclinD1的表达来调控细胞周期,通过加强c．iun氨基端激酶活性和激活Caspase-3来促进紫外线诱导的癌细胞凋亡以及通过影响肌动蛋白聚合重组来改变肿瘤细胞运动和侵袭能力等。此外还有HU1对NPM1的双向调节、转录因子YY1增强HLJ1启动子活性、HU1调控钙黏蛋白E和CIM4等下游基因表达的研究。HLJ1基因在肿瘤发生发展中作用机制的阐明可为下一步的科学研究和临床应用提供新思路。     

p53 negatively regulates Pin1 expression under ER stress

Accumulating evidence suggests that endoplasmic reticulum (ER) stress plays a major role in the development of many diseases. A previous study indicated that the apoptotic regulator p53 is significantly increased in response to ER stress and participates in ER stress-induced apoptosis. However, the regulators of p53 expression during ER stress are still not fully understood. Here, we investigated whether p53 contributes to the impairment of Pin1 signaling under ER stress. We found that treatment with thapsigargin, a stimulator of p53 expression and an inducer of ER stress, decreased Pin1 expression in HCT116 cells. Also, we identified functional p53 response elements (p53REs) in the Pin1 promoter. Overexpression of p53 significantly decreased Pin1 expression in HCT116 cells while abolition of p53 gene expression induced Pin1 expression. Pin1 expression was significantly increased by treatment with the p53 inhibitor pifithrin-α or down-regulation of p53 expression. Taken together, ER stress decreased Pin1 expression through p53 activation, and this mechanism may be associated with ER stress-induced cell death. These data reported here support the importance of Pin1 as a potential target molecule mediating tumor development.     

Pharmacological activation of a novel p53-dependent S-phase checkpoint involving CHK-1

We have recently shown that induction of the p53 tumour suppressor protein by the small-molecule RITA (reactivation of p53 and induction of tumour cell apoptosis; 2,5-bis(5-hydroxymethyl-2-thienyl)furan) inhibits hypoxia-inducible factor-1α and vascular endothelial growth factor expression in vivo and induces p53-dependent tumour cell apoptosis in normoxia and hypoxia. Here, we demonstrate that RITA activates the canonical ataxia telangiectasia mutated/ataxia telangiectasia and Rad3-related DNA damage response pathway. Interestingly, phosphorylation of checkpoint kinase (CHK)-1 induced in response to RITA was influenced by p53 status. We found that induction of p53, phosphorylated CHK-1 and γH2AX proteins was significantly increased in S-phase. Furthermore, we found that RITA stalled replication fork elongation, prolonged S-phase progression and induced DNA damage in p53 positive cells. Although CHK-1 knockdown did not significantly affect p53-dependent DNA damage or apoptosis induced by RITA, it did block the ability for DNA integrity to be maintained during the immediate response to RITA. These data reveal the existence of a novel p53-dependent S-phase DNA maintenance checkpoint involving CHK-1.     

MiR-155 promotes proliferation of human breast cancer MCF-7 cells through targeting tumor protein 53-induced nuclear protein 1

Background

MiR-155 has emerged as an “oncomiR”, which is the most significantly up-regulated miRNA in breast cancer. However, the mechanisms of miR-155 functions as an oncomiR are mainly unknown. In this study, the aims were to investigate the effects of miR-155 on cell proliferation, cell cycle, and cell apoptosis of ERalpha (+) breast cancer cells and to verify whether TP53INP1 (tumor protein 53-induced nuclear protein 1) is a target of miR-155, and tried to explore the mechanisms of miR-155 in this process.

Results

The expression of miR-155 is significantly higher in MCF-7 cells compared with MDA-MB-231 cells. Ectopic expression of TP53INP1 inhibits growth of MCF-7 cells by inducing cell apoptosis and inhibiting cell cycle progression. Overexpression of miR-155 increases cell proliferation and suppress cell apoptosis, whereas abrogating expression of miR-155 suppress cell proliferation and promotes cell apoptosis of MCF-7 cells. In addition, miR-155 negatively regulates TP53INP1 mRNA expression and the protein expression of TP53INP1, cleaved-caspase-3, -8, -9, and p21, and luciferase reporter reveals that TP53INP1 is targeted by miR-155.

Conclusions

TP53INP1 is the direct target of miR-155. MiR-155, which is overexpressed in MCF-7 cells, contributes to proliferation of MCF-7 cells possibly through down-regulating target TP53INP1.     

Long noncoding RNA VCAN-AS1 contributes to the progression of gastric cancer via regulating p53 expression

Gastric cancer (GC) is one of the most frequent malignancies worldwide. Long noncoding RNAs (lncRNAs) are found to be largely implicated in various cancers, including GC. However, the function of lncRNA VCAN antisense RNA 1 (VCAN-AS1) in GC remains unclear. Herein, we observed a low level of VCAN-AS1 in normal gastric tissues through NCBI and UCSC, and that VCAN-AS1 upregulation in GC tissues was related to poor prognosis by TCGA. Furthermore, VCAN-AS1 was found markedly enhanced in GC tissues and cell lines, while its upregulation was related with clinical outcomes of GC patients. Besides this, silencing VCAN-AS1 represses cell proliferation, migration, and invasion but enhances apoptosis. More important, we discovered that VCAN-AS1 expression was negatively correlated with wild-type p53 levels in GC tissues and that p53 was negatively modulated by VCAN-AS1 in GC cells. Furthermore, p53 suppression reversed the repression of VCAN-AS1 silence on the biological processes of AGS cells. Intriguingly, we identified that both VCAN-AS1 and TP53 can bind with eIF4A3, one of the core proteins in the exon junction complex. Also, we confirmed that VCAN-AS1 negatively regulates TP53 expression by competitively binding with eIF4A3. Our findings disclosed that VCAN-AS1 contributes to GC progression through interacting with eIF4A3 to downregulate TP53 expression, indicating that VCAN-AS1 is a novel therapeutic strategy for GC treatment.