A truncated recombination repeat in the mitochondrial genome of a Petunia CMS line

Repeated sequences known as recombination repeats are present in the majority of plant mitochondrial genomes. Two recombination repeat sequences from Petunia have been analyzed. The two repeats are virtually identical over 1.42 kb. One of the repeats is truncated and is likely to have arisen from a rare recombination event in the full-length repeat. Two sequence-blocks within the Petunia repeat are highly similar to sequences in the 5 flank of several plant mitochondrial genes. No sequence motifs are shared by the Petunia repeat and other sequenced plant mitochondrial recombination repeats, suggesting that the recombination occurs by an homologous, rather than a site-specific, mechanism.     

Repair of plasmid DNA used for transformation of <Emphasis Type="Italic">Rhizopus oryzae</Emphasis> by gene conversion

Techniques for genetic manipulation of the filamentous fungus Rhizopus have been hampered due to a lack of understanding regarding the recombination and replication mechanisms that affect the fate of introduced DNA. The ability to target chromosomal integration of a plasmid has been difficult because DNA transformed into Rhizopus rarely integrates and is autonomously replicated in a high molecular weight concatenated arrangement (i.e., series or chain). Linearization of the plasmid prior to transformation at a site having homology with the genomic DNA yields the highest frequency of integration, but repair of the double-strand break by end-joining is still the predominant event. We recently attempted to circumvent replication of the plasmid by introducing frameshift mutations in pyrG, the R. oryzae orotidine-5-monophosphate decarboxylase gene used for selection of the vector. It was hypothesized that autonomous replication of the mutated plasmids would be incapable of restoring prototrophic growth, since the genomic pyrG also contained a mutation. However, homologous integration of the plasmid results in duplication of the pyrG gene, which can create a functional copy of pyrG if both the genomic and plasmid mutations are paired on the same duplicate copy. While this event was detected in one of the isolates, it represented less than 8% of the total transformants. The majority of transformants contained plasmid replicating autonomously in a concatenated arrangement. Sequence analysis showed that prototrophic growth was restored by repairing the non-functional pyrG sequence in the plasmid, while the genomic pyrG gene was unaltered. Frequent transfer of the genomic pyrG mutation to the plasmid suggests that gene conversion is likely occurring by recombination pathways involving break-induced replication or synthesis-dependent strand annealing.USDA: Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

重组水蛭素Ⅲ工程菌菌种稳定性考察

研究基因工程菌E.coli ASl. 357在LB培养基中传代50代过程中菌种的稳定性.以菌体和菌落的形态、质粒稳定性(ST)、质粒酶切图谱和水蛭素的表达量以及比活等方面进行考察,以评价工程菌的稳定性.重组水蛭素Ⅲ工程菌在传代50代的过程中质粒稳定性高,传代10代内质粒稳定性(ST)为98%,且表达稳定,表达产物可达发酵液可溶性蛋白总量的60%,产物的抗凝血酶活力大于2.0×103ATU/ml,传代50代的菌体与菌落呈典型的大肠杆菌形态.重组水蛭素Ⅲ工程菌菌种稳定.     

人乳头瘤病毒16 E7基因的原核表达及表达条件的优化

目的:构建pET-28a(+)-HPV16 E7原核表达质粒,并对其表达条件进行优化,为进一步研究HPV16E7致病机制及HPV疫苗提供相应的技术平台。方法:应用基因重组技术,构建pET-28a(+)与HPV16 E7(标准株和湖北株)的原核表达重组质粒,用PCR、限制性内切酶酶切和核酸序列检测对重组质粒DNA进行鉴定,将其转入宿主菌E.coliBL21(DE 3)进行诱导以表达蛋白;SDS-PAGE及Western blot检测鉴定表达蛋白的分子量及特异性。优化诱导表达的条件,如温度、IPTG浓度、适用的培养基,探讨不同温度下蛋白的表达形式;纯化回收HPV16 E7蛋白。结果:PCR、限制性内切酶酶切和核酸序列检测证实重组质粒中插入的目的基因,其DNA大小、方向、插入位点和阅读框架均正确;HPV16 E7(标准株)蛋白得到高效原核表达,最佳表达条件:表达HPV16 E7的工程菌BL21(DE 3)的最佳诱导温度是37℃,诱导剂IPTG的浓度为0.3-0.4 mmol/L,最佳培养基为1.5倍LB。结论:pET-28a(+)-HPV16 E7标准株和湖北株重组载体构建成功,人乳头瘤病毒16 E7标准株获得高效原核表达。     

Insights into ovarian cancer care: report from the ANZGOG Ovarian Cancer Webinar Series 2020

Epithelial ovarian cancer (EOC) is among the top ten causes of cancer deaths worldwide, and is one of the most lethal gynecological malignancies in high income countries, with incidence and death rates expected to rise particularly in Asian countries where ovarian cancer is among the 5 most common cancers. Despite the plethora of randomised clinical trials investigating various systemic treatment options in EOC over the last few decades, both progression-free and overall survival have remained at approximately 16 and 40 months respectively. To date the greatest impact on treatment has been made by the use of poly (ADP-ribose) polymerase (PARP) inhibitors in women with advanced EOC and a BRCA1/2 mutation. Inhibition of PARP, the key enzyme in base excision repair, is based on synthetic lethality whereby alternative DNA repair pathways in tumor cells that are deficient in homologous recombination is blocked, rendering them unviable and leading to cell death. The Australia New Zealand Gynaecological Oncology Group (ANZGOG) is the national gynecological cancer clinical trials organization for Australia and New Zealand. ANZGOG''s purpose is to improve outcomes and quality of life for women with gynecological cancer through cooperative clinical trials and undertaking multidisciplinary research into the causes, prevention and treatments of gynecological cancer. This review summarizes current ovarian cancer research and treatment approaches presented by Australian and New Zealand experts in the field at the 2020 ANZGOG webinar series entitled “Ovarian Cancer systems of Care”.     

携带野生型PTEN基因的腺病毒载体的构建

目的 构建携带野生型PFEN(Phosphatase and tensinhomolog deleted on chromosome ten)基因的腺病毒载体,为研究PFEN功能和作用机制提供手段。方法将野生型PFEN基因克隆入含有绿色荧光蛋白(Green fluorescence protein,GFP)基因的pAdTrack-CMV质粒,在含有pAdEasy-1病毒骨架的BJ5183大肠杆菌内进行同源重组;重组子通过脂质体介导转染AD293细胞,并在AD293细胞内包装为具有感染能力的病毒颗粒;通过反复感染扩增病毒以达到感染靶细胞的适当滴度,通过GFP表达来监控腺病毒扩增;Western blot检测靶细胞内PFEN蛋白的表达。结果感染腺病毒载体的AD293细胞表达GFP,随着时间逐渐增强,并且出现明显的细胞病变效应(Cytopathic effect,CPE),经过3轮扩增,病毒达到合适的滴度。受腺病毒感染心肌细胞内PTEN蛋白表达明显增高。结论成功构建了携带PFEN基因的腺病毒载体。     

人免疫缺陷病毒1型CRF07_BC毒株准种间的重组

目的 通过研究人类免疫缺陷病毒1型（human immunodeficiency virus1，HIV-1）感染者个体内准种间的差异，探讨HIV的系统进化的发生模式。方法 从HIV-1感染者血浆中提取总RNA，通过逆转录多聚酶链反应（RT-PCR）获得HIV．1gp120全长基因，纯化后装入T载体，转化至TOP10大肠埃希菌内增殖，通过蓝白斑筛选获得阳性克隆，对所获得的目的克隆测序并分析。结果 获得同一患者的16个克隆的gp120全长基因序列，通过系统进化树分析，克隆序列均为CRF07_BC亚型，但在系统进化树上16个克隆可明显分为A、B两群，其中13个克隆属于A群，2个克隆属于B群，1个克隆（编号XPD7）位于A、B群之间，通过simplot软件的重组分析，发现XPD7克隆为A群和B群的重组株。结论 发现了我国广泛流行的HIV-1CRF07-BC毒株准种间的重组现象，准种间的重组作为HIV进化的一种有效手段将导致HIV毒株的快速进化的发生，可能更易逃脱宿主的免疫监控。     

结核分枝杆菌特异性抗原重组蛋白MPT63检测系统的建立

[目的]建立规范的结核分枝杆菌（mycobacterium tuberculosis，MTB）特异性抗原重组蛋白MPT63酶联免疫吸附试验（enzyme—linked immunosorbent assay，ELISA）检测系统。[方法]采用方阵法确定蛋白包被浓度和酶标二抗浓度，以ROC（Receiver Operating Characteristic）曲线法确定MPT63蛋白ELISA法检测的cut—off值。探讨规范的ELISA检测系统建立的方法。[结果]ELISA检测系统MPT63蛋白包被浓度1：128000，酶浓度1：1000时为最佳；在cut—off值为0．35—0．4时检测MPT63蛋白抗体的灵敏度和特异性最为理想，分别是75％和78．6％。[结论]用方阵法确定蛋白包被浓度和酶标二抗浓度，并以ROC曲线法确立cut—off值是建立规范化的ELISA检测系统的关键环节。