B lineage--specific interactions of an immunoglobulin enhancer with cellular factors in vivo

The mouse heavy chain immunoglobulin gene contains a tissue-specific enhancer. The enhancer and flanking sequences were studied in vivo by carrying out dimethyl sulfate protection experiments on living cells, in combination with genomic sequencing. Relative to reactions on naked DNA, there are changes (protections and enhancements) in the reactivity of guanine residues to dimethyl sulfate within the enhancer sequence in myeloma, B, and early B cells, whereas virtually no alterations appear in cells of non-B lineage. Most of the affected residues are in four clusters, in sequences homologous to the octamer 5'CAGGTGGC 3' (C, cytosine; A, adenine; G. guanine; T, thymine). The alterations in the pattern of G reactivity are consistent with the tissue-specific binding of molecules to the mouse immunoglobulin heavy chain enhancer.     

Contribution of promoter to tissue-specific expression of the mouse immunoglobulin kappa gene

The immunoglobulin kappa (kappa) gene promoter was activated by a "neutral" enhancer derived from Harvey murine sarcoma virus (HaMuSV) in immunoglobulin-producing myeloma cells, regardless of the enhancer's orientation or position in the vector. In one fibroblast line (3T3) the immunoglobulin kappa gene promoter was completely inactive when linked to the HaMuSV enhancer, whereas in mouse L cells, promoter activity was observed only with the HaMuSV enhancer in tandem with the immunoglobulin kappa gene promoter. The differential behavior of the gene promoter, when activated by a neutral enhancer in these three murine cell lines, suggests that promoter sequences contribute to the tissue-specific expression of this gene.     

桉树葡萄糖-6-磷酸脱氢酶(G6PDH)的全基因组分析与进化研究

[目的]对桉树基因组中葡萄糖-6-磷酸脱氢酶（G6PDH）进行全基因组分析与进化研究。[方法]利用巨桉（Eucalyptus grandsis）全基因组数据,采用BLAST等生物信息学软件分析桉树G6PDH的基因特性、蛋白序列、系统进化树以及启动子特征。[结果]桉树基因组内存在6个G6PDH基因,其编码蛋白中,1个为胞质型G6PDH,5个为质体型G6PDH,而且桉树G6PDH均含有保守基序motif 1、motif 2、motif 3、motif 7、motif 9和motif 11。此外,桉树G6PDH启动子序列中均存在TATA框、增强子与涉及光应答、激素应答、胁迫应答等调控元件。[结论]可为下一步研究桉树G6PDH家族基因的分子功能提供参考。     

假蒟甲醇提取物的抑制真菌作用

[目的]研究假蒟甲醇提取物对几种植物病原菌的抑制作用。[方法]采用生长速率法测定假蒟叶甲醇提取物对香蕉炭疽病菌等9种植物病原真菌的生物活性。[结果]假蒟叶甲醇提取物在2mg／ml的浓度下,对9种菌有一定的抑制率,对香蕉炭疽病菌、番木瓜炭疽病菌、香蕉枯萎病菌、西瓜蔓枯病菌的半数有效浓度（EC50）分别为0．7849,0．7663、0．8913、1．6425mg／ml。假蒟叶甲醇提取物的石油醚、乙酸乙酯和正丁醇萃取组分对香蕉炭疽病菌和番木瓜炭疽病菌的活性表明,乙酸乙酯萃取物活性最高,抑制率分别为72．7％和88．3％。假蒟甲醇提取物的乙酸乙酯萃取物对香蕉炭疽病菌和番木瓜炭疽病菌的髓EC50分别为0．5692,0．5446mg/ml。[结论]证实假蒟叶甲醇提取物中含有具有抑真菌活性的次生物质,该物质溶于石油醚、乙酸乙酯、正丁醇等有机溶剂。     

Chitin-induced dimerization activates a plant immune receptor

Pattern recognition receptors confer plant resistance to pathogen infection by recognizing the conserved pathogen-associated molecular patterns. The cell surface receptor chitin elicitor receptor kinase 1 of Arabidopsis (AtCERK1) directly binds chitin through its lysine motif (LysM)-containing ectodomain (AtCERK1-ECD) to activate immune responses. The crystal structure that we solved of an AtCERK1-ECD complexed with a chitin pentamer reveals that their interaction is primarily mediated by a LysM and three chitin residues. By acting as a bivalent ligand, a chitin octamer induces AtCERK1-ECD dimerization that is inhibited by shorter chitin oligomers. A mutation attenuating chitin-induced AtCERK1-ECD dimerization or formation of nonproductive AtCERK1 dimer by overexpression of AtCERK1-ECD compromises AtCERK1-mediated signaling in plant cells. Together, our data support the notion that chitin-induced AtCERK1 dimerization is critical for its activation.     

桉树葡萄糖-6-磷酸脱氢酶（G6PDH）的全基因组分析与进化研究

[目的]对桉树基因组中葡萄糖-6-磷酸脱氢酶（G6PDH）进行全基因组分析与进化研究。[方法]利用巨桉（Eucalyptus grandsis）全基因组数据,采用BLAST等生物信息学软件分析桉树G6PDH的基因特性、蛋白序列、系统进化树以及启动子特征。[结果]桉树基因组内存在6个G6PDH基因,其编码蛋白中,1个为胞质型G6PDH,5个为质体型G6PDH,而且桉树G6PDH均含有保守基序motif1、motif2、motif3、motif7、motif9和motif11。此外,桉树G6PDH启动子序列中均存在TATA框、增强子与涉及光应答、激素应答、胁迫应答等调控元件。[结论]可为下一步研究桉树G6PDH家族基因的分子功能提供参考。     

鸡传染性支气管炎病毒单克隆抗体的制备及鉴定

用纯化的鸡传染性支气管炎病毒免疫BALB／c小鼠,取其脾细胞与骨髓瘤细胞Ag8．653融合。对杂交瘤细胞及时筛选,阳性孔经3次有限稀释法克隆,成功获得3株能稳定传代并分泌抗鸡传染性支气管炎病毒单克隆抗体的杂交瘤细胞株1F4F7D9、3E9G3D4、48883F8。通过间接ELISA、血凝抑制以及琼脂糖扩散等方法检测,3株单克隆抗体的腹水间接ELISA效价达10^6以上并且具有良好的特异性。     

2种拟补骨脂素化合物室内抑菌活性测定

[目的]为了测定2种拟补骨脂素化合物F(a)、S(b)的室内抑菌活性。[方法]采用菌丝生长速率法进行测定。[结果]化合物F(a)、S(b)对供试植物病原真菌均有较好的抑制作用,其中化合物F(a)对8种植物病原菌的EC50均小于58.00mg/L,其中对苹果炭疽病菌抑制效果最好,EC50仅为12.74mg/L;化合物S(b)对8种植物病原菌的EC50均小于63.00mg/L,其中对葡萄白腐病菌抑制效果最好,EC50为18.61mg/L;化合物F(a)、S(b)对其他植物病原菌也具有较好的抑制作用。[结论]该研究为今后研制开发新型仿生农药奠定了基础。     

超高压对单核细胞增生李斯特氏菌细胞膜损伤 及其氧化磷酸化的影响

 【目的】研究超高压作用对单核细胞增生李斯特氏菌(LM 54004)细胞膜、氧化磷酸化和F0F1-ATP酶的影响。【方法】用原子吸收法测定LM 54004经超高压作用后细胞内金属离子(K+、Mg2+)的泄漏;以亲脂性阳离子四苯基溴化膦 ([3H]-TPP+) 作为放射性探针标记LM 54004细胞膜,测定经超高压作用后细胞膜电位的变化;用羧基荧光素琥珀酰亚胺酯 (cFSE)为荧光探针测定经超高压作用后细胞内pH的变化;用比色法测定超高压对LM 54004 F0F1-ATP酶活性的影响。【结果】150—300 MPa作用10 min,随着压力的增大LM 54004菌落数显著降低,细胞内K+和Mg2+没有泄漏到细胞外,膜电势、跨膜H+浓度梯度和质子动力势大小基本保持不变,F1F0-ATP酶活性降低显著;300 MPa作用10 min,尽管LM 54004菌落数低于检测限,F0F1-ATP酶活性降到0,但细胞膜完整无损,其质子动力势仍然达到最大值。【结论】超高压作用下LM 54004的灭活与F0F1-ATP酶活性的降低之间相关性较好。LM 54004的细胞膜上参与呼吸链有关的酶和电子载体较F0F1-ATP酶耐压,F0F1-ATP酶对超高压敏感,超高压作用下F0F1-ATP酶的失活是超高压灭活的重要原因。     

Crystallographic structure of the octameric histone core of the nucleosome at a resolution of 3.3 A

The structure of the (H2A-H2B-H3-H4)2 histone octamer has been determined by means of x-ray crystallographic techniques at a resolution of 3.3 angstroms. The octamer is a prolate ellipsoid 110 angstroms long and 65 to 70 angstroms in diameter, and its general shape is that of a rugby ball. The size and shape are radically different from those determined in earlier studies. The most striking feature of the histone octamer is its tripartite organization, that is, a central (H3-H4)2 tetramer flanked by two H2A-H2B dimers. The DNA helix, placed around the octamer in a path suggested by the features on the surface of the protein, appears like a spring holding the H2A-H2B dimers at either end of the (H3-H4)2 tetramer.