Novel DNA binding proteins highly specific to UV-damaged DNA sequences from embryos of Drosophila melanogaster.

Three new proteins which selectively bind to UV-damaged DNA were identified and purified to near homogeneity from UV-irradiated Drosophila melanogaster embryos through several column chromatographies. These proteins, tentatively designated as D-DDB P1, P2 and P3, can be identified as different complex bands in a gel shift assay by using UV-irradiated TC-31 probe DNA. Analysis of the purified D-DDB P1 fraction by native or SDS-polyacrylamide gel electrophoresis and FPLC-Superose 6 gel filtration demonstrated that it is a monomer protein which is a 30 kDa polypeptide. The D-DDB P2 protein is a monopolypeptide with a molecular mass of 14 kDa. Both D-DDB P1 and P2 highly prefer binding to UV-irradiated DNA, and have almost no affinity for non-irradiated DNA. Gel shift assays with either UV-irradiated DNA probes demonstrated that D-DDB P1 may show a preference for binding to (6-4) photoproducts, while D-DDB P2 may prefer binding to pyrimidine dimers. Both these proteins require magnesium ions for binding. D-DDB P1 is an ATP-preferent protein. These findings are discussed in relation to two recently described [Todo and Ryo (1991) Mutat. Res., 273, 85-93; Todo et al. (1993) Nature, 361, 371-374] DNA-binding factors from Drosophila cell extracts. A possible role for these DNA-binding proteins in lesion recognition and DNA-binding proteins in lesion recognition and DNA repair of UV-induced photo-products is discussed.     

巴拉巴按蚊人工交配中雄蚊蚊龄与受精率的关系

自McDaniel和Horsfall(1957)介绍了伊蚊的人工交配法后,许多原来在实验室内不易自然交配,因而无法繁殖的蚊种,已可在室内大量繁殖以供实验研究之用。1966年Esah和Scanlon用人工交配法,在室内饲养巴拉巴按蚊获得成功。国内四川医学院及成都生物制品研究所亦于1976年在室内同时建立了海南白沙巴拉巴按蚊品系。由于工作的需要,我们通过人工交配对该蚊种进行了饲养繁殖。但在多次人工交配中,雌蚊受精率常不一致,有时只有30％左右,有时则可高达80％以上。这种受精率的不稳定是否与雄蚊蚊龄有相应关系?为此,我们用羽化后12天以内不同日龄的雄蚊,分别进行了人工交配,以观察雄蚊日龄与其对雌蚊授精率之间,有无必然的相应关系。     

十三种农田常见步(虫甲)的食性

步科昆虫食性比较复杂,有的种类猎食害虫,有的为害农作物。所以,在天敌昆虫资源调查和开发利用上,有必要查明农田步(虫甲)的种类和它们的食性。鉴于多种步(虫甲)喜土栖而夜出活动,其经济意义难以了解,我们于1980—1981年间,采取室内饲养试验的方法,初步查明13种农田常见步(虫甲)的食性及其猎食对象。现简要报道如下。     

表观遗传修饰介导的植物胁迫记忆

植物因其固着生长的方式, 已经进化出各类特殊的机制来适应多变的外界环境。为提高自身的存活率, 植物进化出一类胁迫记忆机制, 以适应环境和保护自己。表观遗传修饰不仅能调控植物的正常生长发育, 而且参与植物对各种非生物或生物胁迫的响应。近年的研究表明, 表观遗传修饰在植物胁迫记忆调控中也发挥重要作用。例如, DNA甲基化、组蛋白甲基化及乙酰化等表观遗传修饰参与并维持特定的胁迫记忆。该文主要对表观遗传修饰介导的植物胁迫记忆最新进展进行综述, 并展望未来的重点和热点研究方向。     

Crystallization and main-chain structure of neutral protease from Streptomyces caespitosus

A neutral protease, i.e., a zinc-containing metalloendoprotease from Streptomyces caespitosus, has been crystallized using acetone as a precipitating agent. The crystals diffract to better than 1.5 A resolution when a rotating anode X-ray generator is used as an X-ray source. Protein phase angles were calculated by the multiple isomorphous replacement method using two heavy-atom derivatives (HgCl2 and CH3HgCl). A 6 A resolution electron density map clearly showed molecular boundaries. Although its amino acid sequence is not known, the folding pattern of the polypeptide chain could be traced on a 2.5 A resolution electron density map. A large cleft, which is located on the molecular surface, was proved to be the active site of the enzyme by structure analyses of inhibitor-complex crystals. The highest electron density peak, which corresponds to the cleft, was assigned to a catalytically essential zinc atom on difference Fourier synthesis between native and EDTA-soaked crystals.     

中华按蚊在实验室内的自然交配习性

1973年我们在上海曾对宝山县中华按蚊(Anopheles sinensis)进行了室内饲养,通过自然交配繁殖了8代。1975年又对重庆郊区的中华按蚊同样地进行了室内累代饲育。近几年来文献上报道:未经驯化的中华按蚊,在实验室内常规饲养条件下,不易发生自然交配(Oguma和Kanda,1976;潘家复和韩罗珍,1979)。这一报道与我们的经验很不一致。为了弄清引起这种不一致的原因,以便改进饲养工作,我们特别对第一代中华按蚊在实验室内自然交配的某些规律,进行了观察。现将观察结果报告如下。