phP53-luc质粒的构建及其用于检测化学物质遗传毒性的初步分析

目的:构建2个分别由p53基因启动子和核心启动子驱动的荧光素酶报告基因表达质粒,并探讨其用于检测遗传毒性化学物质的可行性.方法:通过PCR扩增人p53基因启动子片段,然后采用重组DNA技术克隆入pGL3-BASIC的荧光素酶报告基因的上游而获得phP53-luc表达质粒.用脂质体转染法将phP53-luc转染入NIH 3T3细胞并分别用5-氟尿嘧啶(5-FU)处理,最后裂解细胞用Dual-Luciferase Reporter Assay System检测荧光素酶报告基因表达.结果:构建了2个分别由p53基因启动子和核心启动子驱动的荧光素酶报告基因表达质粒,位于这2个质粒上的荧光素酶报告基因在NIH 3T3细胞内的表达显著地受遗传毒性化学物质的诱导,其表达比对照的pGL3-BASIC载体上的荧光素酶报告基因高近240倍.结论:基于人p53基因启动子的荧光素酶报告基因分析系统可以用于快速检测环境毒物的遗传毒性.     

虫荧光色素酶报告基因重组腺病毒表达载体的构建与鉴定

目的:构建表达虫荧光色素酶报告基因重组腺病毒载体,为腺病毒中和抗体流行水平的定量检测奠定基础?方法:采用腺病毒表达系统(ViraPower Adenoviral Expression System)构建重组腺病毒表达载体?首先利用PCR的方法扩增虫荧光色素酶基因使其具备特定的CACC接头,以连接?转化?提取质粒等方法克隆入载体pENTR/D-TOPO以获得入门克隆,经PCR及测序鉴定正确后,用重组酶(LR ClonaseTMⅡ Enzyme Mix)进行入门克隆与表达载体(pAd-CMV/V5-DEST)间的重组反应,以获得表达克隆rAd-Luci?表达克隆鉴定后,用限制性内切酶PacⅠ线性化后转染HEK293A包装细胞得到重组腺病毒?经过扩增后,用极限稀释法检测病毒滴度,用Western blot法检测rAd-Luci载体是否能正确表达虫荧光色素酶蛋白,并检测此酶蛋白的功能活性?结果:用PCR的方法扩增到具有CACC接头的虫荧光色素酶基因,其重组入门和腺病毒表达克隆经PCR和测序鉴定构建正确,重组表达克隆转染HEK293A细胞并扩增后获得的病毒滴度为1.8×1011 pfu/ml,此病毒能正确表达虫荧光色素酶蛋白,并且具有较强的功能活性?结论:成功构建了虫荧光色素酶报告基因重组腺病毒载体,为此重组载体用于腺病毒中和抗体的定量检测奠定基础?     

IDO启动序列GAS和ISRE荧光素酶报告基因载体构建及其活性检测

目的构建pGL3-Enhancer-ISRE4和pGL3-Enhancer-GAS两个荧光素酶报告基因载体,并对其进行生物活性鉴定。方法通过人工合成调控吲哚胺2,3-双加氧酶（IDO）表达的启动序列ISRE4（4个串联的ISRE序列）和GAS7（7个串联的GAS序列）,与pGL3-Enhancer连接成重组体pGL3-Enhancer-ISRE4和pGL3-Enhancer-GAS7,通过转化扩增,筛选出阳性克隆,并通过酶切、测序及生物学活性检测鉴定构建好的荧光素酶报告基因载体。结果成功地构建了pGL3-Enhancer-ISRE4和pGL3-Enhancer-GAS7两个荧光素酶报告基因载体,在IFN-γ的诱导下,能启动细胞内荧光素酶的表达。结论 pGL3-Enhancer-ISRE4和pGL3-Enhancer-GAS7的荧光素酶报告基因载体的成功构建为研究IDO蛋白的表达调控机制和以IDO为靶标的抗肿瘤免疫耐受药物快速高通量的筛选提供了重要的研究工具。     

Development of a Cell-Based Luciferase Complementation Assay for Identification of SARS-CoV-2 3CLpro Inhibitors

The 3C-like protease (3CL^pro) of SARS-CoV-2 is considered an excellent target for COVID-19 antiviral drug development because it is essential for viral replication and has a cleavage specificity distinct from human proteases. However, drug development for 3CL^pro has been hindered by a lack of cell-based reporter assays that can be performed in a BSL-2 setting. Current efforts to identify 3CL^pro inhibitors largely rely upon in vitro screening, which fails to account for cell permeability and cytotoxicity of compounds, or assays involving replication-competent virus, which must be performed in a BSL-3 facility. To address these limitations, we have developed a novel cell-based luciferase complementation reporter assay to identify inhibitors of SARS-CoV-2 3CL^pro in a BSL-2 setting. The assay is based on a lentiviral vector that co-expresses 3CL^pro and two luciferase fragments linked together by a 3CL^pro cleavage site. 3CL^pro-mediated cleavage results in a loss of complementation and low luciferase activity, whereas inhibition of 3CL^pro results in 10-fold higher levels of luciferase activity. The luciferase reporter assay can easily distinguish true 3CL^pro inhibition from cytotoxicity, a powerful feature that should reduce false positives during screening. Using the assay, we screened 32 small molecules for activity against SARS-CoV-2 3CL^pro, including HIV protease inhibitors, HCV protease inhibitors, and various other compounds that have been reported to inhibit SARS-CoV-2 3CL^pro. Of these, only five exhibited significant inhibition of 3CL^pro in cells: GC376, boceprevir, Z-FA-FMK, calpain inhibitor XII, and GRL-0496. This assay should greatly facilitate efforts to identify more potent inhibitors of SARS-CoV-2 3CL^pro.     

Mast cells derived from human induced pluripotent stem cells are useful for allergen tests

Background

Several methods have been developed to detect allergen-specific IgE in sera. The passive IgE sensitization assay using human IgE receptor-expressing rat cell line RBL-2H3 is a powerful tool to detect biologically active allergen-specific IgE in serum samples. However, one disadvantage is that RBL-2H3 cells are vulnerable to high concentrations of human sera. Only a few human cultured cell lines are easily applicable to the passive IgE sensitization assay. However, the use of human induced pluripotent stem cells (iPSCs) to generate human mast cells (MCs) has not yet been reported.

Rhythmic adenosine triphosphate release from the cyanobacterial circadian clock protein KaiC revealed by real-time monitoring of bioluminescence using firefly luciferase

The cyanobacterial circadian clock is composed of three clock proteins, KaiA, KaiB and KaiC. This KaiABC clock system can be reconstituted in vitro in the presence of adenosine triphosphate (ATP) and Mg²⁺, and shows circadian rhythms in the phosphorylation level and ATPase activity of KaiC. Previously, we found that ATP regulates a complex formation between KaiB and KaiC, and KaiC releases ATP from KaiC itself (PLoS One, 8, 2013, e80200). In this study, we examined whether the ATP release from KaiC shows any rhythms in vitro. We monitored the release of ATP from wild-type and ATPase motif mutants of KaiC as a bioluminescence in real time using a firefly luciferase assay in vitro and obtained the following results: (a) ATP release from KaiC oscillated even without KaiA and KaiB although period of the oscillation was not 24 hr; (b) ATP was mainly released from the N-terminal domain of KaiC; and (c) the ATP release was enhanced and suppressed by KaiB and KaiA, respectively. These results suggest that KaiC can generate basal oscillation as a core clock without KaiA and KaiB, whereas these two proteins contribute to adjusting and stabilizing the oscillation.     

大鼠Caspase 8基因启动子荧光素酶报告质粒的构建及其与IRF-1结合位点的鉴定

目的:构建大鼠Caspase 8基因启动子(全长和截短)荧光素酶报告质粒,并观察在人胚肾细胞(HEK293)中,过表达干扰素调节因子-1(interferon regulatory factor-1,IRF-1)对Caspase 8基因启动活性的影响?同时,筛选其可能的IRF-1结合位点?方法:采用PCR技术,扩增出大鼠Caspase 8基因启动子序列(-1136~+101 nt),将Caspase 8基因启动子插入到荧光素酶报告基因载体pGL3-basic中?将Caspase 8基因启动子全长荧光素酶报告质粒(pGL3-Caspase 8-FL)和大鼠野生型IRF-1表达质粒(pcDNA3.1-IRF-1)共转染HEK293细胞,检测其荧光素酶活性,确定IRF-1对Caspase 8基因的启动作用?另用生物信息学软件预测Caspase 8基因启动子上IRF-1潜在的结合位点,并构建Caspase 8基因启动子截短的荧光素酶报告质粒(即pGL3-Caspase 8-1~4)?将上述Caspase 8基因启动子全长和各截短的荧光素酶报告质粒和IRF-1过表达质粒共转染HEK293细胞,再行荧光素酶活性测定,筛选IRF-1的结合位点?结果:菌液PCR及核酸测序证实,上述荧光素酶报告质粒均构建成功?将pGL3-Caspase 8-FL和pcDNA3.1-IRF-1共转染HEK293细胞发现,Caspase 8基因启动子活性显著增加?而将pGL3-Caspase 8-FL?pGL3-Caspase 8-1~4和pcDNA3.1-IRF-1共转染HEK293细胞后证实,pGL3-Caspase 8-4的启动活性显著低于pGL3-Caspase 8-2和pGL3-Caspase 8-3?提示IRF-1可能结合在Caspase 8基因启动子的-336~-136 nt区域?结论:本实验成功构建了大鼠Caspase 8基因启动子全长及截短荧光素酶报告质粒,并初步筛查出IRF-1在Caspase 8基因启动子上的结合区域?     

构建p53双荧光报告载体及其功能验证

目的：构建p53双荧光报告载体,验证其能否模拟野生型p53的生物学活性并适用于高通量筛选。方法：用PCR在p53和萤火虫荧光素酶的开放阅读框两端引入酶切位点并移除p53的终止密码和萤火虫荧光素酶的起始密码,然后将二者插入到由内部核糖体进入位点引导的海肾荧光素酶的上游,从而构建出一个能表达P53萤火虫荧光素融合蛋白的p53FL/IRES/RL双荧光报告载体。转染该报告载体后,检测被表达的P53荧光素融合蛋白是否被MDM2降解、该融合蛋白的亚细胞定位和它对p53特异性启动子的诱导。结果：成功构建出p53双荧光报告载体。该载体在宿主细胞内表达的P53荧光素融合蛋白能被MDM2降解;主要分布于细胞核;具有野生型p53的转录活性。结论：新构建的p53双荧光报告载体p53FL/IRES/RL能有效模拟野生型p53的功能,适用于高通量筛选调节P53蛋白含量的药物、基因或化合物。