ATM activation by DNA double-strand breaks through the Mre11-Rad50-Nbs1 complex

The ataxia-telangiectasia mutated (ATM) kinase signals the presence of DNA double-strand breaks in mammalian cells by phosphorylating proteins that initiate cell-cycle arrest, apoptosis, and DNA repair. We show that the Mre11-Rad50-Nbs1 (MRN) complex acts as a double-strand break sensor for ATM and recruits ATM to broken DNA molecules. Inactive ATM dimers were activated in vitro with DNA in the presence of MRN, leading to phosphorylation of the downstream cellular targets p53 and Chk2. ATM autophosphorylation was not required for monomerization of ATM by MRN. The unwinding of DNA ends by MRN was essential for ATM stimulation, which is consistent with the central role of single-stranded DNA as an evolutionarily conserved signal for DNA damage.     

Resonant formation of DNA strand breaks by low-energy (3 to 20 eV) electrons

Most of the energy deposited in cells by ionizing radiation is channeled into the production of abundant free secondary electrons with ballistic energies between 1 and 20 electron volts. Here it is shown that reactions of such electrons, even at energies well below ionization thresholds, induce substantial yields of single- and double-strand breaks in DNA, which are caused by rapid decays of transient molecular resonances localized on the DNA's basic components. This finding presents a fundamental challenge to the traditional notion that genotoxic damage by secondary electrons can only occur at energies above the onset of ionization, or upon solvation when they become a slowly reacting chemical species.     

Size-Specific Infrared Spectra of Benzene-(H2O)n Clusters (n = 1 through 7): Evidence for Noncyclic (H2O)n Structures

Resonant ion-dip infrared spectroscopy has been used to record size-specific infrared spectra of C(6)H(6)-(H(2)O)n clusters with n = 1 through 7 in the O-H stretch region. The O-H stretch spectra show a dramatic dependence on cluster size. For the n = 3 to 5 clusters, the transitions can be divided into three types-attributable to free, pi hydrogen-bonded, and single donor water-water O-H stretches-consistent with a C(6)H(6)-(H(2)O)n structure in which benzene is on the surface of a cyclic (H(2)O)n cluster. In n = 6 and 7 clusters, the spectra show distinct new transitions in the 3500 to 3600 wave number region. After comparison of these results with the predictions of ab initio calculations on (H(2)O)n clusters, these new transitions have been assigned to double donor O-H stretches associated with the formation of a more compact, noncyclic structure beginning with (H(2)O)(6). This is the same size cluster for which ab initio calculations predict that a changeover to noncyclic (H(2)O)n structures will occur.     

Structural basis for DNA damage-dependent poly(ADP-ribosyl)ation by human PARP-1

Poly(ADP-ribose) polymerase-1 (PARP-1) (ADP, adenosine diphosphate) has a modular domain architecture that couples DNA damage detection to poly(ADP-ribosyl)ation activity through a poorly understood mechanism. Here, we report the crystal structure of a DNA double-strand break in complex with human PARP-1 domains essential for activation (Zn1, Zn3, WGR-CAT). PARP-1 engages DNA as a monomer, and the interaction with DNA damage organizes PARP-1 domains into a collapsed conformation that can explain the strong preference for automodification. The Zn1, Zn3, and WGR domains collectively bind to DNA, forming a network of interdomain contacts that links the DNA damage interface to the catalytic domain (CAT). The DNA damage-induced conformation of PARP-1 results in structural distortions that destabilize the CAT. Our results suggest that an increase in CAT protein dynamics underlies the DNA-dependent activation mechanism of PARP-1.     

Molecular cloning of a complementary DNA encoding human macrophage-specific colony-stimulating factor (CSF-1)

Complementary DNA (cDNA) clones encoding human macrophage-specific specific colony-stimulating factor (CSF-1) were isolated. One cDNA clone codes for a mature polypeptide of 224 amino acids and a putative leader of 32 amino acids. This cDNA, which was cloned in the Okayama-Berg expression vector, specifies the synthesis of biologically active CSF-1 in COS cells, as determined by a specific radioreceptor assay, macrophage bone marrow colony formation, and antibody neutralization. Most of the cDNA isolates contain part of an intron sequence that changes the reading frame, resulting in an abrupt termination of translation; these cDNA's were inactive in COS cells. The CSF-1 appears to be encoded by a single-copy gene, but its expression results in the synthesis of several messenger RNA species, ranging in size from about 1.5 to 4.5 kilobases.     

紫云英新品系84(8)7-1-1扩繁表现及留种栽培技术

介绍了紫云英新品系84(8)7-1-1扩繁表现,并总结其留种扩繁技术。     

pYLTAC7载体在水稻品种农垦58S转化中应用的研究

利用TAC(transformation-competent artificial chromosome)载体pYLTAC7，将明恢63的35kb基因组片段通过农杆菌介导的方法导人水稻品种农垦58S中，对pYLTAC7载体直接用于水稻遗传转化的可行性进行了探索性研究。本试验中，pYLTAC7载体转化效率为10．1％，转基因植株R代PCR及Southern分析表明，外源片段已稳定整合到基因组中，从而证明pYLTAC7载体可以在水稻遗传转化中应用。     

产纤维素酶渤海丝状真菌ZDTJ097-1-(7)的筛选及产酶研究

[目的]筛选产纤维素酶渤海丝状真菌ZDTJ097-1-(7),并对其产酶条件和活性进行分析研究。[方法]从渤海湾水域获得的25株丝状真菌中,通过刚果红鉴别法和纤维素酶活性的比较,筛选出1株高产纤维素酶的菌株,并在发酵培养基的基础上,通过改变氮源、培养温度、初始pH值、通气量和接种量等因素,以及不同的反应温度和pH值,以酶的活性为检测指标,探究不同培养条件及反应条件对酶活性的影响。[结果]菌种ZDTJ097-1-(7)在以CMC-Na为唯一碳源的培养基中,可诱导活性较强的滤纸酶、CMC酶和β-葡萄糖苷酶,且在0.5%CMC-Na、0.2%NH4NO3、pH 6.0、25℃条件下,产酶能力最强。酶的最适反应温度为60℃,最适pH值为6.0。[结论]为该菌的进一步开发应用提供了试验依据。     

盐胁迫下盐穗木DNA甲基化程度与去甲基化酶基因(Ros1)表达的相关性研究

【目的】甲基化和去甲基化协同调控的DNA甲基化直接影响逆境胁迫相关基因的表达,植物的DNA去甲基化主要由去甲基化酶基因Ros1(Repressor of Silencing 1)介导的碱基切除修复实现。开展盐穗木(Halostachys caspica)DNA甲基化程度与HcRos1表达动态变化的分析,有助于阐明DNA甲基化应答盐胁迫的分子机制。【方法】利用qRT-PCR测定盐胁迫下盐穗木幼苗同化枝和根基因组DNA的甲基化程度,探讨DNA的甲基化程度与去甲基化酶基因HcRos1表达的相关性。【结果】在相同NaCl浓度胁迫不同时间下盐穗木同化枝和根中DNA甲基化程度呈现先升高后降低的趋势,盐穗木同化枝中的DNA甲基化程度大多高于根中的基因组甲基化程度,且均在24 h达到最高DNA甲基化程度。而在不同浓度NaCl胁迫处理24 h时,盐穗木同化枝和根中DNA甲基化程度也是先升高后降低的趋势,盐穗木同化枝中的基因组甲基化程度高于根中的基因组甲基化程度,且多在100 mmol/L达到最高DNA甲基化程度。HcRos1的基因表达量在低浓度NaCl胁迫下变化不大,但在700 mmol/L NaCl胁迫72 h时则显著升高。【结论】HcRos1表达量与DNA甲基化水平呈明显的负相关,盐胁迫能够提高HcRos1的表达,降低基因组DNA的甲基化程度,增强植物的耐盐性。     

盐穗木醛脱氢酶基因HcALDH7A1原核表达载体的构建及蛋白诱导表达与优化

[目的]为构建盐穗木盐响应基因HcALDH7A1的原核表达载体并进行外源基因的诱导表达和优化.[方法]以实验室已构建好的p mD18-T Simple-HcALDH7A1/DH5α(Pst Ⅰ,SacⅠ)重组载体中盐穗木醛脱氢酶基因(HcALDH7A1)为模板,设计带有酶切位点(EcoRⅠ,XhoⅠ)的引物通过PCR扩增亚克隆到p mD18-TSimple vector中,测序鉴定正确后,通过EcoRⅠ和Xho Ⅰ双酶切,构建重组的原核表达载体pET28a-HcALDH7 A1.将鉴定正确的重组质粒转化到大肠杆菌Transetta(DE3)中,经异丙基-β-D-硫代半乳糖苷(IPTG)诱导表达,SDS-PAGE检测目的蛋白表达,并对其表达体系进行优化.[结果]成功构建盐穗木醛脱氢酶基因HcALDH7A1的原核表达载体,诱导HcALDH7A1外源基因表达蛋白优化的最佳条件为IPTG终浓度为0.6 mmol/L,30℃诱导时间为4h.融合蛋白分子量大小为61 kD.[结论]成功在大肠杆菌体内诱导表达盐穗木醛脱氢酶HcALDH7A1基因,并明确目的蛋白的最佳表达条件.为后续在原核表达系统大肠杆菌细胞中探索盐穗木HcALDH7A1的生物和非生物胁迫的功能奠定了基础.     

2-辛亚砜-5,8-二甲氧基-1,4萘醌通过ROS/Akt通路诱导HepG2细胞凋亡

为研究修饰后的萘醌类衍生物对人肝癌细胞株HepG2诱导细胞凋亡作用及其机制。采用MTT、流式和Western blot方法观察2-辛亚砜-5,8-二甲氧基-1,4萘醌对人肝癌细胞的生长作用。结果表明:2-辛亚砜-5,8-二甲氧基-1,4萘醌可通过促进早期ROS水平升高,抑制Akt的磷酸化水平,并选择性地激活p38,ERK信号通路,从而抑制肝癌细胞株HepG2细胞的增殖并诱导其发生凋亡。     

猪繁殖与呼吸综合征病毒S-1株ORF5和ORF7基因的克隆及变异分析

PRRSV S-1株经Marc-145复苏后,通过RT-PCR扩增了ORF5和ORF7基因.利用酶切位点将2个基因分别连接到原核表达载体PET-32C中,筛选阳性克隆送测序,序列分析表明:PRRSV S-1株ORF5基因变异性较高,与VR-2332毒株和CH-1a毒株的同源性分别是:核苷酸同源性为91%和89%,氨基酸同源性是87%和85%;ORF7基因相对保守,核苷酸的同源性分别是97%和94%,氨基酸的同源性分别是95%和93%.     

河八王杂交种F1、BC1及其亲本DNA甲基化水平和模式变化

为分析河八王及后代基因组DNA甲基化水平和遗传模式变化,以河八王及其后代F_1和BC_1为材料,采用甲基化敏感扩增多态性技术(Methylation sensitive amplification polymorphism,MSAP)结合毛细管电泳技术(Capillary electrophoresis,CE)分析亲本及后代基因组DNA甲基化水平和遗传模式变化规律。结果表明:母本‘GT05-3256’的MSAP比率是59.6%,父本‘GXN1’则是60.5%,其杂交种F_1的MSAP比率是56.4%～59.0%,均低于双亲;BC_1的母本‘YC94-46’的MSAP比率是59.4%,父本‘T6-3’则是59.0%,BC_1MSAP比率是56.9%～69.8%,整体平均为62.8%,平均值高于双亲。BC_1世代总甲基化水平略高于F_1世代水平。F_1和BC_1基因组CCGG位点发生甲基化的方式整体上以内部胞嘧啶双链甲基化为主。在F_1和BC_1中均检测到70种甲基化类型,并进一步分为A、B、C、D和E等5大类,其中A类是亲本向杂交种的甲基化遗传类型;B类是去甲基化类型,表示杂交种相应于其亲本的甲基化减弱;C类是过或超甲基化类型,表示杂交种相应于其亲本的甲基化增强;D类是次甲基化类型,杂交后代甲基化水平比双亲均要低;E类为不定类型。结果显示,B、C、D、E是杂交种的甲基化变异类型;F_1的甲基化遗传类型(A类)比例明显低于BC_1,但变异类型B、C、D、E高于BC_1;杂交形成F_1和BC_1过程中,基因组DNA普遍发生了超甲基化修饰。     

重组禽流感病毒H5+H7亚型三价灭活疫苗（H5N1Re-11株、Re-12株+H7N9Re-2）对蛋鸡免疫效果抗体监测以及安全性试验评估

试验通过对重组禽流感病毒(H5+H7)三价灭活疫苗(H5N1Re-11株+Re-12株+H7N9 H7Re2株)在接种蛋鸡后产生抗体效价值的情况,评价重组禽流感病毒(H5+H7)三价灭活疫苗(H5N1Re-11株+Re-12株+H7N9 Re-2株)对蛋鸡预防高致病性禽流感疫病的效果。同时进行安全性试验。结果表明,蛋鸡在15日龄接种重组禽流感病毒(H5+H7)三价灭活疫苗(H5N1Re-11株+Re-12株+H7N9 H7Re2株),45日龄进行二次免疫,75日龄进行三免,产生H5N1Re-11株抗体滴度、H5N1Re-12株抗体滴度、H7N9 Re-2株抗体滴度都较高,从抗体消长规律来看,对产蛋前的蛋鸡都有较好的保护力,疫苗接种后未对鸡群造成应激反应。通过本试验在蛋鸡上接种重组禽流感病毒(H5+H7)三价灭活疫苗(H5N1Re-11株+Re-12株+H7N9 H7Re2株)首次免疫后14 d产生抗体有保护力,二免后14 d抗体滴度达到高峰,对蛋鸡有很好的保护力,为预防蛋鸡高致病性禽流感疫病提供临床依据。     

梅花鹿茸生长过程中顶端不同组织COL1A1基因启动子DNA甲基化模式及差异分析

为探究COL1A1基因表达的Ⅰ型胶原蛋白α1链在组成生物体结构和骨发育中的重要作用,以梅花鹿茸生长过程的小鞍子（前期）、二杠（中期）和三杈茸（后期）3个典型时期鹿茸顶端组织及其茸皮、间充质、前软骨和软骨4个组织层为试验材料,采用亚硫酸氢盐测序法（BSP技术）,从时空角度研究鹿茸生长过程中顶端不同组织COL1A1基因启动子区DNA甲基化模式及其相互间DNA甲基化差异。结果显示：1)COL1A1基因在前、中、后期的茸皮组织中的甲基化率分别为（9.73±0.92）%、（7.60±0.69）%和（3.73±0.23）%;间充质组织中的甲基化率分别为（3.20±0.40）%、（1.33±0.23）%和（1.60±0.69）%;前软骨组织中的甲基化率分别为（4.67±0.83）%、（2.53±0.46）%和（2.67±0.23）%;软骨组织中的甲基化率分别为（5.60±0.40）%、（2.80±0.40）%和（2.27±0.61）%。2)COL1A1基因启动子区的甲基化区域共有25个CG位点,在17个CG位点上均发生了不同程度的甲基化。3）对COL1A1基因启动子区DNA甲基化差异分析发现,相同时...     

Protective efficacy of an H5/H7 trivalent inactivated vaccine (H5-Re13, H5-Re14, and H7-Re4 strains) in chickens,ducks, and geese against newly detected H5N1, H5N6, H5N8, and H7N9 viruses

Some H5 viruses isolated in poultry or wild birds between 2020 and 2021 were found to be antigenically different from the vaccine strains(H5-Re11 and H5-Re12) used in China. In this study, we generated three new recombinant vaccine seed viruses by using reverse genetics and used them for vaccine production. The vaccine strain H5-Re13 contains the hemagglutinin(HA) and neuraminidase(NA) genes of an H5 N6 virus that bears the clade 2.3.4.4 h HA gene, H5-Re14 contains the HA and NA genes of an H5 N...     

Genetic Diversity of <Emphasis Type="Italic">E. coli O157:H7</Emphasis> Isolated from Some Leafy Greens,Irrigated by Aleppo River,Using Random Amplified Polymorphic DNA (RAPD) Marker

In recent years, fresh fruits and vegetables have been linked to numerous foodborne illness outbreaks in different regions of the world. In Syria, there is not a lot of research that study E. coli and its serotypes by PCR technology. In this study, we have fulfilled a total count of bacteria, the census total coliform group, and Escherichia coli, as well as the serotype E. coli O157:H7 on some leafy greens (Spinacia oleracea, Beta vulgaris) irrigated by Aleppo River. The molecular characterization was done for ten strains of E. coli isolated from collected samples. The samples were inoculated on blood agar and suspicious colonies, then transferred to EMB and MacConkey agar using a primer (COL 1) in RAPD technic. Molecular characterization also performed ten strains of serotype E. coli O157:H7 isolated in medium (Sorbitol-MacCONKEY Agar), then by primers (OPA-03, OPA-13 OPC-12, OPE-20) in RAPD technic. The results showed significant differences between collected samples. The total count of bacteria in the first site (Handarat) for spinach and chard were the lowest, but in the fourth site (Jezraya) it was the highest among all samples. The results showed also the existence of E. coli in all sites except the first one in riverbed Handarat, and E. coli O157:H7 was found only in Jezraya village. Extracted DNA from samples was amplified by RAPD. after electrophoresis in the gel agarose, eleven different bands were detected from isolated strains of E. coli. These results refer to the great genetic diversity of Escherichia coli. For serotype E. coli O157:H7 thirty-four different bands were detected. RAPD analysis had the high discriminatory capacity for typing E. coli isolates. Because of its simplicity and rapidity, RAPD analysis appears to be a highly valuable tool for studying E. coli molecular epidemiology.