UHRF2, a Ubiquitin E3 Ligase,Acts as a Small Ubiquitin-like Modifier E3 Ligase for Zinc Finger Protein 131

Small ubiquitin-like modifier (SUMO), a member of the ubiquitin-related protein family, is covalently conjugated to lysine residues of its substrates in a process referred to as SUMOylation. SUMOylation occurs through a series of enzymatic reactions analogous to that of the ubiquitination pathway, resulting in modification of the biochemical and functional properties of substrates. To date, four mammalian SUMO isoforms, a single heterodimeric SUMO-activating E1 enzyme SAE1/SAE2, a single SUMO-conjugating E2 enzyme ubiquitin-conjugating enzyme E2I (UBC9), and a few subgroups of SUMO E3 ligases have been identified. Several SUMO E3 ligases such as topoisomerase I binding, arginine/serine-rich (TOPORS), TNF receptor-associated factor 7 (TRAF7), and tripartite motif containing 27 (TRIM27) have dual functions as ubiquitin E3 ligases. Here, we demonstrate that the ubiquitin E3 ligase UHRF2 also acts as a SUMO E3 ligase. UHRF2 effectively enhances zinc finger protein 131 (ZNF131) SUMOylation but does not enhance ZNF131 ubiquitination. In addition, the SUMO E3 activity of UHRF2 on ZNF131 depends on the presence of SET and RING finger-associated and nuclear localization signal-containing region domains, whereas the critical ubiquitin E3 activity RING domain is dispensable. Our findings suggest that UHRF2 has independent functional domains and regulatory mechanisms for these two distinct enzymatic activities.     

High-density array analysis of DNA methylation in Tamoxifen-resistant breast cancer cell lines

Roughly two-thirds of all breast cancers are ERα-positive and can be treated with the antiestrogen, Tamoxifen, however resistance occurs in 33% of women who take the drug for more than 5 y. Aberrant DNA methylation, an epigenetic mechanism that alters gene expression in cancer, is thought to play a role in this resistance. To develop an understanding of Tamoxifen-resistance and identify novel pathways and targets of aberrant methylation, DNA from MCF-7 breast cancer cells and Tamoxifen-resistant derivatives, TMX2–11 and TMX2–28, were analyzed using the Illumina HumanMethylation450 BeadChip. Normalizing against MCF-7 values, ERα-positive TMX2–11 had 4000 hypermethylated sites and ERα-negative TMX2–28 had over 33?000. Analysis of CpG sites altered in both TMX2–11 and TMX2–28 revealed that the Tamoxifen-resistant cell lines share 3000 hypermethylated and 200 hypomethylated CpGs. ZNF350 and MAGED1, two genes hypermethylated in both cell lines, were examined in greater detail. Treatment with 5-aza-2′deoxycitidine caused a significant reduction in promoter methylation of both ZNF350 and MAGED1 and a corresponding increase in expression in TMX2–28. A similar relationship between methylation and expression was not detected in TMX2–11. Our findings are indicative of the variable responses to methylation-targeted breast cancer therapy and highlight the need for biomarkers that accurately predict treatment outcome.     

Regulation of cell proliferation and migration in gallbladder cancer by zinc finger X-chromosomal protein

Gallbladder carcinoma (GBC) is one of the mostly aggressive and fatal malignancies. However, little is known about the oncogenic genes that contributed to the development of GBC. Zinc finger X-chromosomal protein (ZFX) was a novel member of the Krueppel C2H2-type zinc-finger protein family and its down-regulation led to impaired cell growth in human laryngeal squamous cell carcinoma. Here, we aim to investigate the function of ZFX in GBC cell proliferation and migration. Loss of function analysis was performed on GBC cell line (GBC-SD) using lentivirus-mediated siRNA against ZFX. The proliferation, in vitro tumorigenesis (colony-formation) ability as well as cell migration was significantly suppressed after GBC-SD cells which were infected with ZFX-siRNA-expressing lentivirus (Lv-shZFX). Our finding suggested that ZFX promoted the growth and migration of GBC cells and could present a potential molecular target for gene therapy of GBC.     

DNA甲基化通过锌指蛋白185调控慢性粒细胞白血病细胞的增殖

锌指蛋白185(ZNF185)属于LIM结构域蛋白,参与细胞的增殖和分化,在多种肿瘤细胞中具有抑癌基因的功能.ZNF185在正常人血液系统细胞中高表达,但目前对白血病细胞的作用未见研究.采用Western blot检测人外周血中性粒细胞、急性粒细胞白血病细胞系HL-60和慢性粒细胞白血病细胞系K562细胞中ZNF185的表达,发现ZNF185在HL-60和K562细胞中的表达水平显著低于外周血中性粒细胞.为了阐明ZNF185对慢性粒细胞白血病细胞增殖的影响,从人外周血中性粒细胞克隆ZNF185编码序列,转染K562细胞,MTT检测细胞增殖,发现过表达ZNF185显著抑制K562细胞的增殖.甲基化特异PCR分析表明:ZNF185启动子在HL-60和K562细胞中高甲基化,用5-氮杂-2′-脱氧胞苷处理K562细胞,促进ZNF185的表达,显著抑制细胞增殖.研究结果表明,ZNF185启动子高甲基化导致其在K562细胞中的表达降低和细胞增殖抑制作用减弱.可能是慢性粒细胞白血病发生或发展的原因之一.     

Deoxyribonuclease 1-like 3 Inhibits Hepatocellular Carcinoma Progression by Inducing Apoptosis and Reprogramming Glucose Metabolism

HCC has remained one of the challenging cancers to treat, owing to the paucity of drugs targeting the critical survival pathways. Considering the cancer cells are deficient in DNase activity, the increase of an autonomous apoptisis endonuclease should be a reasonable choice for cancer treatment. In this study, we investigated whether DNASE1L3, an endonuclease implicated in apoptosis, could inhibit the progress of HCC. We found DNASE1L3 was down-regulated in HCC tissues, whereas its high expression was positively associated with the favorable prognosis of patients with HCC. Besides, serum DNASE1L3 levels were lower in HCC patients than in healthy individuals. Functionally, we found that DNASE1L3 inhibited the proliferation of tumor cells by inducing G0/G1 cell cycle arrest and cell apoptosis in vitro. Additionally, DNASE1L3 overexpression suppressed tumor growth in vivo. Furthermore, we found that DNASE1L3 overexpression weakened glycolysis in HCC cells and tissues via inactivating the rate-limiting enzymes involved in PTPN2-HK2 and CEBPβ-p53-PFK1 pathways. Finally, we identified the HBx to inhibit DNASE1L3 expression by up-regulating the expression of ZNF384. Collectively, our findings demonstrated that DNASE1L3 could inhibit the HCC progression through inducing cell apoptosis and weakening glycolysis. We believe DNASE1L3 could be considered as a promising prognostic biomarker and therapeutic target for HCC.