乳腺癌易感蛋白BRCA1的BRCT2结构域染色质伸展活性的定位

40 %～ 5 0 %的遗传性乳腺癌和至少 80 %的既有乳腺癌又有卵巢癌家族史的患者是由BRCA1突变引起的 .BRCA1C末端含有 2个BRCT结构域 (BRCT1和BRCT2 ) ,它们与BRCA1的重要功能密切相关 .许多乳腺癌易感突变发生在BRCA1的BRCT结构域中 .利用染色质结构检测技术表明 ,BRCT结构域具有染色质伸展活性 .利用缺失突变技术构建了 6种BRCT2结构域 (175 6～ 185 2位氨基酸残基 )缺失突变体并将BRCT2结构域中与染色质伸展相关的重要区域定位到 175 6～ 180 8之间的氨基酸残基 ;用丙氨酸扫描技术构建了 6种BRCT2结构域丙氨酸扫描突变体并将重要氨基酸残基序列定位到 1784～ 1788之间的VQLCG .BRCT2结构域的定位有助于预测BRCT2结构域突变后发生乳腺癌的风险 ,也为进一步研究BRCT2结构域的功能机制提供了有用的材料 .     

乳腺癌易感蛋白BRCA1的BRCT1结构域染色质伸展活性的定位

乳腺癌易感基因BRCA1（Breast cancer susceptibility gene 1）在乳腺癌的发生、发展中起重要作用。BRCA1 C末端含有2个BRCT结构域（BRCT1和BRCT2）,许多乳腺癌易感突变发生在BRCA1的BRCT结构域中。利用染色质结构检测技术表明,BRCT结构域具有染色质伸展活性。本文利用缺失突变技术构建了6种BRCT1结构域（1642-1736 aa）缺失突变体并将BRCT1结构域中与染色质伸展相关的重要区域定位到1691-1721之间的氨基酸残基;用丙氨酸扫描技术构建了10种BRCT1结构域丙氨酸扫描突变体并将重要氨基酸残基序列定位到1707-1711之间的IAGGK。利用定位的重要区域进行Blast分析,结果找到一新型同源蛋白质。BRCT1结构域的定位有助于预测BRCT1结构域突变后发生乳腺癌的风险,也为进一步研究BRCT1结构域的功能机制提供了有用的材料。     

乳腺癌易感基因BRCA1的研究进展

BRCA1基因是目前发现的外显率最高的乳腺癌易感基因之,编码一个相对分子质量为220000的多功能核蛋白,作用于一系列维持基因组稳定性的细胞通路,包括DNA损伤修复、细胞周期检验点激活、蛋白泛素化、染色质重组,以及转录调控和凋亡等。BRCA1丢失将导致显著的遗传不稳定性和生长停滞。着重介绍近年来BRCA1基础研究方面的进展,并讨论BRCA1与乳腺癌的临床关联性。     

乳腺癌易感基因BRCA1研究进展

BRCA1是目前所发现的最重要的乳腺癌易感基因之一,它在DNA损伤修复,细胞周期调节,基因的转录激活,染色质稳定性,细胞增殖等方面都起着重要作用。该文着重介绍近几年来BRCA1基础研究方面的进展,并讨论BRCA1在肿瘤发生、发展过程的作用。为BRCA1在临床上的应用提供理论依据。     

BRCA1基因与乳腺癌

乳腺癌易感基因1(BRCA1)是具有遗传倾向的乳腺癌和卵巢癌的易感基因,且是一种抑癌基因.BRCA1基因的突变与家族性乳腺癌及它在细胞周期的调节,DNA损伤修复,基因的转录调控和诱导细胞凋亡方面起着重要作用.BRCA1基因的突变与家族性乳腺癌及卵巢癌的发生密切相关,对BRCA1分子功能的研究,将有利于阐明肿瘤发生的机理关.BRCA1的启动子甲基化与散发性乳腺癌有关.本文拟对BRCA1的结构,功能以及它的甲基化,突变,杂合性丢失对乳腺癌的影响作一综述.     

扩展青霉脂肪酶K56R叠加突变对热稳定性的影响

目的:扩展青霉脂肪酶随机突变体ep8是一株热稳定性比野生型有所提高的突变体.获得热稳定性提高的优良菌株.方法:在ep8的基础上利用重叠延伸PCR构建叠加突变重组质粒pPIC3.5K-ep8一K56R,将该质粒电转毕赤酵母(Pichia paaoris)GS115进行异源表达.结果:该叠加突变脂肪酶在毕赤酵母中获得了活性表达.15%SDS-PACE结果分析表明突变脂肪酶PEL-ep8-K56R-GS分子量与野生型PEL-GS一致,约为28kDa.叠加突变脂肪酶在37℃时酶活为852U/mL、野生型为760u/mL、随机突变体为824u/mL,叠加突变体酶活相比野生型提高了21.1%,相比随机突变体提高了3.4%.热稳定性分析数据表明叠加突变脂肪酶Tm值为40.1℃、野生型为38.7℃、随机突变体为39.9℃,Tm值相比野生型提高了1.4℃,相比随机突变体提高了0.2℃.     

乳腺癌易感蛋白1在DNA损伤修复中的作用

人类乳腺癌易感基因1(breast cancer susceptibility gene 1,BRCA1)首先是在乳腺癌家族中发现的,是具有遗传倾向的乳腺癌和卵巢癌易感基因,其基因的突变与家族性乳腺癌及卵巢癌的发生有密切联系。BRCA1是一种抑癌基因,其基因产物可以参与维持基因组稳定性的多条细胞信号通路,例如DNA损伤诱导的细胞周期调控、DNA损伤修复、基因转录调节、细胞凋亡、泛素化等重要的细胞活动。本文就近几年来BRCA1在DNA损伤修复中的作用的研究进展作一综述,包括DNA损伤诱导的细胞周期检查点的激活和DNA损伤修复两方面。     

FHL2转录激活结构域的定位

LIM蛋白家族成员FHL2 (fourandhalfLIMdomainprotein)在转录调节、细胞凋亡及肿瘤的发生发展中都起着重要作用。利用GAL4转录因子中的DNA结合结构域 (DBD)和含有与DBD结合序列的荧光素酶报告基因(GAL4 LUC)构建了哺乳动物细胞转录激活系统 ,并利用该系统定位了FHL2的转录激活结构域。首先将GAL4 DBD序列以正确读框插入到pcDNA3载体的多克隆位点中 ,构建成真核表达载体pDBD ,再将野生型FHL2及其不同片段以正确读框与pDBD中GAL4 DBD序列融合 ,构建成野生型FHL2及其缺失突变体表达载体。将这些表达载体分别瞬时转染 2 93T胚胎肾细胞 ,野生型FHL2及其缺失突变体都得到了表达。利用GAL4 荧光素酶报告基因对野生型FHL2及其不同突变体的转录激活活性检测表明 ,在 2 93T胚胎肾细胞和乳腺癌MCF 7细胞中 ,野生型FHL2具有转录激活活性 ,缺失N端半个LIM结构域使FHL2转录激活活性降低 ,缺失C末端第二个LIM结构域对FHL2的转录激活功能影响不大 ,缺失C末端最后一个LIM结构域则使FHL2的转录激活功能完全丧失 ,而C末端缺失 2个LIM结构域使FHL2转录激活活性又有所恢复。这说明FHL2C末端最后一个LIM结构域对其转录激活功能是必需的 ,而C末端第二个LIM结构域可能对FHL2的转录激活功能有负调控作用 ,这种负调控作用取决于     

K55R与ep8叠加突变对扩展青霉脂肪酶热稳定性的改善

利用重叠延伸PCR对扩展青霉脂肪酶(PEL)基因进行体外定点突变,构建了K55R与随机突变体ep8叠加突变的重组质粒pAO815-ep8-K55R。将该质粒电转化引入毕赤酵母(Pichia pastoris)GS115,进行异源表达。实验结果表明:该叠加突变体在毕赤酵母中获得了活性表达,得到表达产物脂肪酶PEL-ep8-K55R-GS。其表达量为508u/mL,分别约为野生型脂肪酶PEL-GS(627u/mL)的81%,随机突变脂肪酶PEL-ep8-GS(924u/mL)的55%;其比活力为2309.1u/mg,与随机突变脂肪酶PEL-ep8-GS和野生型脂肪酶PEL-GS的相仿。叠加突变脂肪酶PEL-ep8-K55R-GS的最适作用温度为37℃,与野生型脂肪酶PEL-GS和随机突变脂肪酶PEL-ep8-GS一致;其Tm值为41.0℃,比野生型脂肪酶PEL-GS提高了2.3℃,比随机突变脂肪酶PEL-ep8-GS提高了0.8℃。表明叠加突变脂肪酶PEL-ep8-K55R-GS的热稳定性有了进一步的提高。     

葡萄球菌肠毒素 B 突变体的构建及其抗肿瘤活性分析

目的：通过对葡萄球菌肠毒素B（SEB）32位His进行定点突变,获得抑瘤效果显著增强的SEB突变体。方法：利用基因定点突变的方法,将SEB的32位His替换为Asn,将重组质粒转入大肠杆菌中诱导表达,用CM弱阳离子层析柱纯化获得重组蛋白,用SDS-PAGE和Western印迹对其进行鉴定,并用增殖实验检测其丝裂原活性,通过MTS法检测其体外抗肿瘤活性。结果：构建并高效表达了突变体蛋白SEB（H32N）,纯化获得了足够纯度的突变体蛋白;体外实验表明,在相同浓度下,SEB（H32N）的丝裂原活性及体外抗肿瘤活性明显优于野生型SEB。结论：同野生型SEB相比,突变体蛋白SEB（H32N）对肿瘤生长的抑制作用得到了提高。     

六种藓类植物茎的比较解剖学研究

通过对6种藓类植物,即褶叶青藓(Brachythecium salebrosum(Web.et Mohr.)B.S.G.)、湿地匐灯藓(Plagiomnium acutum(Lindb.)Kop.)、侧枝匐灯藓(Plagiomnium maximoviczii(Lindb.)Kop.)、大凤尾藓(Fissidensnobilis Griff.)、大羽藓(Thuidium cymbifolium(Doz.et Molk.)B.S.G.)和大灰藓(Hypnum plumaeforme Wils.)嫩茎和老茎的石蜡切片和显微观察发现,同一藓类植株的嫩茎和老茎,茎结构稳定,不同种藓类植物茎横切面具有不同特征.植物体茎横切面形状、表层细胞的层数、细胞大小和细胞壁厚薄、皮层细胞大小和形状、中轴的有无以及比例等特征可以作为藓类植物的分科分类依据之一.     

Cause of Senescence of Nine Sorts of Flowers

The levels of endogenous phytohormones and respiratory rate in nine sorts of flowers such as Cymbidium faberi Rolfe, Nopalxochia ackermannii Kunth and others were investigated both at full bloom and senescence and meanwhile the effect of exogenous phytohormones on prolonging the blossoms and promoting ethylene production were tested. There is a high content of endogenous ethylene in all the long-lived flowere, about 3–16 folds higer than the short-lived ones. There is a high level of ABA at full blooming flowers of short-lived flowers, in which there is no or only some cytokinins in it, but the ratio of CTK (6BA+zeatin)/ABA is smaller(l.7). The endogenous ABA reached a much higher level at senescence in all nine sorts of flowers, so it is reasonable to consider that it is ABA which plays an important role of regulation in controlling flower's senescence. There is a much higher level of GA3 and zeatin in the long-lived flowers which is not demonstrated in the shortlived ones. The respiratory rate is one of the factors controtling the longevity of flowers, but it does not play a decided role. Application of 6BA and zeatin prolongs distinctly orchid’s longevity, however exogenous IAA through the promotive action on ethylene production, evidently extends the longevity of the flowers of the Nopalxochia ackermannii Kunth.     

龙胆科药用植物化学成分的研究现状

龙胆科植物在我国的分布范围很广,且多数为药用植物,其多数种属的药用植物,至今其化学成分尚未被系统研究。综述了目前龙胆科药用植物的化学成分的研究现状及一般提取方法,对近年来发现的环烯醚萜及裂环烯醚萜类化合物进行了总结,为本科药用植物的更深入研究提供了参考。     

The effects of glutamine of the maintenance of embryogenic cultures of Cryptomeria japonica

Summary Embryogenic tissues of sugi (Cryptomeria japonica) were induced on a modified Campbell and Durzan (CD) medium containing 1 μM 2,4-dichlorophenoxyacetic acid (2,4-D) and 600 mg l⁻¹ glutamine, and subcultured in the medium of the same composition for over 1 yr. This resulted in a mixed culture of embryogenic and non-embryogenic cells. When embryogenic cells were isolated and cultured independently, their capacity to form embryogenic aggregates was lost. Thus, the non-embryogenic cells present within a mixed culture system were essential to the formation of embryogenic aggregates. When embryogenic tissues were isolated and cultured independently on a high glutamine-containing (2400 mg l⁻¹) medium, dry weights and endogenous levels of glutamine increased, and the tissue could generate a large number of embryogenic aggregates. Amino acid analysis of embryogenic and non-embryogenic cells from the maintenance culture indicated a higher level of glutamine was present in the latter. The high endogenous level of glutamine in the non-embryogenic portion of mixed cell masses may be the supplier of glutamine for maintaining the embryogenic property of the tissues.     

Specificity of action of piperidylcholine derivatives as substrates of cholinesterases of various origin

The review deals with study of enzymologic properties of a novel highly specific acetylcholinesterase substrate, N-(β-acetoxyethyl) piperidinium iodomethylate (“piperidylcholine”), and its 30 derivatives that were tested as effectors of cholinesterases of mammals and various species of Pacific squids. It was proven for the first time that responsible for specificity of action was structure of cyclic ammonium grouping of the alcohol part of molecule of the ester substrate. Analysis of specificity is performed based on enzymatic hydrolysis parameters—activity of catalytic center of cholinesterases and bimolecular constant of the reaction rate that are determined at optimal and low substrate concentrations. Among the specially synthesized group of thioester compounds there is revealed one more highly specific acetylcholinesterase substrate—N-(β-acetoxyethyl) piperidinium.     

真菌类遗传学分析的知识结构教学

本文以认知结构理论为指导,讨论了真菌类遗传分析与高等动植物遗传分析的内在联系,认为利用这种内在联系进行教学可收到好的效果并说明了作者的具体教学过程。 Abstract:In the paper, the relationship between genetic analysis of Fungi and genetic analysis of high animal and plant was discussed.A good results were obtained when we adopted this method in the teaching.     

The mechanism of hatching of eggs of Haemonchus contortus

Fluid collected from hatching eggs of Haemonchus contortus contained a lipase which hydrolysed 2-naphthyl laurate (about 0·7 μmol naphthol freed /h/10⁶ eggs). The fluid also hydrolysed l-leucinamide (about 2·3 μmol leucine freed/h/10⁶ eggs). The fluid when added to normal or heated eggs caused ‘hatching’. ‘Hatching’ also occurred in exsheathing fluid from infective juveniles and in a preparation of pancreatic lipase containing leucine aminopeptidase. A purified mammalian leucine aminopeptidase in combination with several different lipases did not attack egg shells.The ‘spontaneous’ hatching of eggs of H. contortus was strongly inhibited by 1,10-phenanthroline, 10^?3M, and this inhibition was reversed by Zn²⁺. However, the inhibition of ‘hatching’ of eggs in externally applied hatching fluid, or the hydrolysis of leucinamide in hatching fluid was generally less marked.     

Photoregulation of seed germination of wild-type and of an aurea-mutant of tomato

Seed germination of an aurea mutant of tomato ( Lycopersicon esculentum Mill.) is promoted by continuous irradiation with red, far-red or long-wavelength far-red (758 nm) light as well as by cyclic irradiations (5 min red or 5 min far-red/25 min darkness). Far-red light applied immediately after each red does not change the germination behaviour. Seed germination of the isogenic wild-type, cv. UC-105, is promoted by continuous and cyclic red light while it is inhibited by continuous and cyclic far-red light and by continious 758 nm irradiation. Far-red irradiation reverses almost completely the promoting effect of red light. The promoting effect (in the aurea mutant) and the inhibitory effect (in the wild-type) of continuous far-red light do not show photon fluence rate dependency above 20 nmol m⁻² s⁻¹. It is concluded that phytochrome controls tomato seed germination throgh low energy responses in both the wild type and the au mutant. The promoting effect of continuous and cyclic far-red light in the au mutant can be attributed to a greater sensitivity to P_fr.