Modeling the Structure of Yeast MAT<i>α</i>1: An HMG-Box Motif with a C-Terminal Helical Extension

The yeast MATα1 is required for the activation of α-specific genes in Saccharomyces cerevisiae and thus confers the α-cell identity of the yeast. MATα1 contains a domain called the α-domain which has significant sequence identity to the HMG-box family of proteins. A multiple sequence alignment of several α-domains and various structurally determined HMG-box domains has revealed that both domains possess very similar structural and functional residues. We found that the basic amino acids of the N-terminal loop, the intercalating hydrophobic residues of the first helix, and the hydrophobic residues required for interactions within the core of the protein are remarkably conserved in α-domains and HMG-box proteins. Our generated molecular models suggest that the first and third helix will be shorter and that the HMG-box core is not an isolated domain. The region beyond the conserved HMG-box motif contains an extended helical region for about 20 - 30 amino acids. Structural models generated by comparative modeling and ab initio modeling reveal that this region will add two or more additional α-helices and will make significant contacts to helix III, II and I of the HMG-box core. We were able to illustrate how the extended α-domain would bind to DNA by merging of the α-domain and the LEF-1/DNA complex. The models we are reporting will be helpful in understanding how MATα1 binds to DNA with its partner MCM1 and activates transcription of α-specific genes. These models will also aid in future biophysical studies of MATα1 including the crystallization and structure determination.

Silencing MTA1 by RNAi Reverses Adhesion, Migration and Invasiveness of Cervical Cancer Cells (SiHa) via Altered Expression of p53, and E-cadherin/β-catenin Complex

It has been reported that metastasis-associated gene 1 （Mta1） is overexpressed in many malignant tumors with high metastatic potential. In addition, some studies indicated that MTA1 participated in invasion, metastasis, and survival of cancer cells by regulating cell migration, adhesion and proliferation. But the role of MTA1 is unclear in vitro in the development of cervical cancer cells. This study investigated whether and how MTA1 mediated cell proliferation, migration, invasion and adhesion in cervical cancer. MTA1 expression level was detected by Western blot in two cervical cancer cell lines of different invasion potentials. The effects of MTA1 expression on SiHa cell apoptosis, cycle, proliferation, migration, invasion and adhesion were tested by flow cytometry, MTT, wound-healing assay, Transwell assay and adhesion assay, respectively. The expression levels of p53, E-cadherin, and β-catenin activity were evaluated in untreated and treated cells. The results showed that MTA1 protein expression was significantly higher in SiHa than in HeLa, which was correlated well with the potential of migration and invasion in both cell lines. Furthermore, the cell invasion, migration and adhesion capabilities were decreased after inhibition of MTA1 expression mediated by Mta1-siRNA transfection in SiHa. However, no significant differences were found in cell apoptosis, cycle, and proliferation. In addition, E-cadherin and p53 protein levels were significantly up-regulated, while β-catenin was significantly down-regulated in SiHa transfected with the siRNA. These results demonstrated that MTA1 played an important role in the migration and invasion of cervical cancer cells. It was speculated that the decreased migration and invasion capability by inhibiting the MTA1 expression in the SiHa cell line may be mediated through the altered expression of p53, and E-cadherin/β-catenin complex. MTA1 could serve as a potential therapeutic target in cervical cancer.

Effect of siRNA Targeting MTA1 on Metastasis Malignant Phenotype of Ovarian Cancer A2780 Cells

Ovarian cancer is the fifth lethal gynecologic malignancy. Metastasis-associated gene 1 （MTA1） is overexpressed in many malignant tumors with high metastatic potential. This study investi- gated whether down-regulation of MTA1 expression by RNAi in A2780 ovarian cancer cells could affect proliferation, anoikis, migration, invasion and adhesion of the cells and to research the potential for MTA1 gene therapy of ovarian cancer. After transfection with effective Mtal gene siRNA, the effects on proliferation, anoikis, migration, invasion and adhesion of A2780 cells were tested by MTT assay, flow cytometry, wound-healing assay, Transwell assay and adhesion assay. Expression levels of PTEN, beta 1 integrin, MMP-9, phosphor-AKT （Ser473）, and total AKT activity were evaluated in control and transfected cells. The results showed that inhibition of MTA1 mediated by Mtal-siRNA transfection decreased the cell invasion, migration and adhesion, and induced the increased cell anoikis, but no significant difference was found in proliferation of A2780 cancer cells. In addition, beta 1 integrin, MMP-9, and phosphor-AKT protein levels were significantly down-regulated, while PTEN was significantly up-regulated. These results demonstrated that MTA1 played an important role in the cell metastasis in ovarian cancer. MTA1 could serve as another novel potential therapeutic target in ovarian cancer.

Detection of Copy Number Alteration of MTA1 in Human Breast Cancer

OBJECTIVE The purpose of our study was to investigate the expression level of MTA1 mRNA in breast cancer and its significance in relation to clinical pathology. METHODS The expression levels of MTA1 mRNA in tumor and in paired normal adjacent tissue of 56 cases with breast cancer were detected by fluorescent quantitative polymerase chain reaction. RESULTS The expression of MTA1 mRNA was detected in 47 tumor specimens of 56 breast cancer patients （83.9%） and was significantly higher than in the paired normal breast tissue. The over expressed MTA1 mRNA was significantly associated with pathologic stage （P = 0.029）, clinical grade （P = 0.035） and lymph node status （P = 0.001）. CONCLUSION The over expression of MTA1 mRNA may play a crucial role in the development of breast cancer. As the MTA1 was comparatively highly-expressed in breast cancer, it may become a new biomarker for the diagnosis and treatment of breast cancer in the future.

苦参碱诱导白血病TF-1细胞凋亡及对SALL4基因表达的影响

目的:探讨苦参碱(matrine,Mat)诱导急性髓性白血病M6型人红白血病TF-1细胞凋亡及对SALL4基因表达的影响。方法:将不同质量浓度(0.5,1.0,1.52,.0 g.L-1)的Mat分别作用于体外培养的TF-1细胞不同时间(24,48,72 h),MTT检测Mat对细胞增殖的影响;流式细胞术(flow cytometry,FCM)测定细胞周期;Annexin V和PI双染色法检测细胞凋亡;逆转录RT-PCR(reverse transcription PCR,RT-PCR)检测SALL4 mRNA表达。结果:Mat(0.5～2.0 g.L-1)作用TF-1细胞24,48,72 h后均有增殖抑制作用(P<0.01),在该浓度范围内抑制率呈剂量和时间依赖4,8 h半数抑制浓度(IC50)为1.0 g.L-1;Mat作用TF-1细胞48 h后,与对照组相比G0/G1期细胞比例增加,S期细胞下降(P<0.01);流式细胞术检测细胞凋亡率分别为8.6%1,1.21%,15.26%,17.63%,与对照组(5.05%)相比较,差异具有统计学意义(P<0.01);RT-PCR结果显示SALL4mRNA表达量与β-actin(内参照)表达量的比值,随Mat剂量增加而显著减小(P<0.01)。结论:Mat在一定浓度和时间范围内对TF-1细胞具有增殖抑制作用,其机制是使细胞发生G0/G1期阻滞;抑制SALL4基因的表达,诱导细胞凋亡。

Bioinformatic exploration of MTAl-regulated gene networks in colon cancer

Metastasis-associated gene 1 （MTA1） controls a series of biological processes in tumor progression. Tumor progression is a complex process regulated by a gene network. The global cancer gene regulatory network must be analyzed to determine the position of MTA1 in the molecular network and its cooperative genes by further exploring the biological functions of this gene. We used TCGA data sets and GeneCards database to screen MTA1- related genes. GO and KEGG pathway analyses were conducted with DAVID and gene network analysis via STRING and Cytoscape. Results showed that in the development of colon cancer, MTA1 is linked to certain signal pathways, such as Wnt/Notch/nucleotide excision repair pathways. The findings also suggested that MTA1 demonstrates the closest relationship in a coregulation process with the key molecules AKT1, EP300, CREBBP, SMARCA4, RHOA, and CAD. These results lead MTAI exploration to an in-depth investigation in different directions, such as Wnt, Notch, and DNA repair.