Comparative genomics of the HOG-signalling system in fungi

Signal transduction pathways play crucial roles in cellular adaptation to environmental changes. In this study, we employed comparative genomics to analyse the high osmolarity glycerol pathway in fungi. This system contains several signalling modules that are used throughout eukaryotic evolution, such as a mitogen-activated protein kinase and a phosphorelay module. Here we describe the identification of pathway components in 20 fungal species. Although certain proteins proved difficult to identify due to low sequence conservation, a main limitation was incomplete, low coverage genomic sequences and fragmentary genome annotation. Still, the pathway was readily reconstructed in each species, and its architecture could be compared. The most striking difference concerned the Sho1 branch, which frequently does not appear to activate the Hog1 MAPK module, although its components are conserved in all but one species. In addition, two species lacked apparent orthologues for the Sln1 osmosensing histidine kinase. All information gathered has been compiled in an MS Excel sheet, which also contains interactive visualisation tools. In addition to primary sequence analysis, we employed analysis of protein size conservation. Protein size appears to be conserved largely independently from primary sequence and thus provides an additional tool for functional analysis and orthologue identification. Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

Saccharomyces cerevisiae: a useful model host to study fundamental biology of viral replication

Understanding the fundamental steps of virus life cycles including virus–host interactions is essential for the design of effective antiviral strategies. Such understanding has been deferred by the complexity of higher eukaryotic host organisms. To circumvent experimental difficulties associated with this, systems were developed to replicate viruses in the yeast Saccharomyces cerevisiae. The systems include viruses with RNA and DNA genomes that infect plants, animals and humans. By using the powerful methodologies available for yeast genetic analysis, fundamental processes occurring during virus replication have been brought to light. Here, we review the different viruses able to direct replication and gene expression in yeast and discuss their main contributions in the understanding of virus biology.     

The relationship between the IC50, toxic threshold, and the magnitude of stimulatory response in biphasic (hormetic) dose–responses

Hormesis is a dose–response relationship characterized by a biphasic (U- or inverted U-shaped) response. We present the results of a study designed to assess the relationship between toxic potency (as measured by the IC₅₀) and the magnitude of the hormesis stimulation. To facilitate this, we describe a new parameter (Δ_X), which we define as the difference between the concentration (or dose) that inhibits 50% of the growth of the organism under study (IC₅₀), and the concentration (or dose) of the respective toxicological threshold (either the benchmark dose (BMD) or zero equivalent point (ZEP)). Our analysis includes a subset of data from a previously published report describing a National Cancer Institute study that exposed yeast to putative anticancer agents in a high throughput assay. The toxic threshold used in this paper was the BMD₅. Thus, the Δ_X in this paper is defined as: Δ_X = IC₅₀ − BMD₅. We have found that the Δ_X and the magnitude of stimulation above the control response are inversely related. These findings describe the first known relationship between toxic potency and the magnitude of hormetic response and warrant further inquiry.     

Isolation, characterization and long term preservation of mutant strains of Xanthophyllomyces dendrorhous

The yeast Xanthophyllomyces dendrorhous is biotechnologically important due to its ability to produce the pigment astaxanthin, but is poorly understood at the genetic level. This is mainly because its preservation is difficult and many of the mutants obtained are unstable. The objectives of the present work were (i) the mutagenesis X. dendrorhous and, (ii) isolation of mutants with auxotrophic markers suitable for genetic studies of the carotenogenesis pathway and sexual cycle. Additionally, two kinds of preservation methods at the laboratory level were tested for the storage of strains. A collection of X. dendrorhous mutants affected in the production of carotenoid pigments or development of sexual structures and auxotrophic requirements were isolated by treatment with N-methyl-N'-nitro-N-nitrosoguanidine and the antibiotic nystatin. From a detailed analysis about the requirements of auxotrophic mutants the ARG7, ARG3 and PRO3 loci can be defined in this yeast. Among the methods assayed for the long-term preservation of X. dendrorhous strains, the dehydrated gelatin drop method showed the highest recovery of viable yeast after storage for 65 months. No changes in auxotrophic properties and in macro or micro morphology were observed after applying the latter method.     

中药富硒酵母对动物中枢免疫器官发育的影响

目的:研究有机硒对动物胸腺和腔上囊的平均重量、器官指数和组织结构发育的影响。方法:取1日龄闽中麻鸡396羽,随机分为4组,对照组(A组)饲喂基础日粮,试验组(B、C、D组)分别在基础日粮中添加中药富硒酵母2、34、g/kg,试验期49 d。每周末各组随机取鸡6羽,称重后处死取胸腺和腔上囊,称重,Bouin液固定,制作石蜡切片,显微观察,摄影。结果:B、C、D组的胸腺和腔上囊平均质量和器官指数均高于A组,部分差异显著(P<0.05)或极显著(P<0.01)。D组鸡胸腺小叶增大,皮质增厚,胸腺小体减少;C组腔上囊皱襞发达,腔上囊小结体积较大,皮质较厚,退化迟缓。结论:在动物基础日粮中添加中药富硒酵母能够促进动物胸腺和腔上囊的发育。添加0.201 mg/kg有机硒对腔上囊发育有明显的促进作用;添加0.268 mg/kg的有机硒对胸腺的发育有促进作用,延缓胸腺的退化。     

不同造模剂诱导大鼠高尿酸血症模型的可行性比较

目的比较三种高尿酸血症大鼠模型的可行性。方法实验大鼠随机分为三个造模组和对照组。造模组分别予5%氧嗪酸钾(5%OA)饲料、10%酵母粉(10%YE)饲料、10%酵母粉+2%氧嗪酸钾(10%YE+2%OA)饲料饲养3周后予普通饲料饲养1周,对照组予普通饲料。各周留取大鼠血、尿标本,检测尿酸、肌酐、尿素氮、白蛋白、甘油三酯、胆固醇等指标的变化。结果与对照组相比,5%OA组血尿酸在各周均升高(P<0.05);10%YE组血尿酸仅在第2周升高(P<0.05);10%YE+2%OA组血尿酸在第1、2周升高(P<0.05),第3周下降至正常。造模组与对照组的体重、血清肌酐、血清尿素氮、血清白蛋白水平无差异。结论 5%OA模型可形成较稳定的高尿酸血症状态,10%YE模型难以达到高尿酸血症状态,10%YE+2%OA模型血尿酸水平欠稳定。     

Peptide aptamer mimicking RAD51-binding domain of BRCA2 inhibits DNA damage repair and survival in Trypanosoma brucei

The eukaryotic DNA recombination repair protein BRCA2 is functional in the parasitic protozoan Trypanosoma brucei. The mechanism of the involvement of BRCA2 in homologous recombination includes its interaction with the DNA recombinase proteins of the RAD51 family. BRCA2 is known to interact with RAD51 through its unique and essential BRC sequence motifs. T. brucei BRCA2 homolog (TbBRCA2) has fifteen repeating BRC motifs as compared to mammalian BRCA2 that has only eight. We report here our yeast 2-hybrid analysis studies on the interactions of TbBRCA2 BRC motifs with five different RAD51 paralogues of T. brucei. Our study revealed that a single BRC motif is sufficient to bind to these RAD51 paralogues. To test the possibility whether a single 44 amino acid long repeating unit of the TbBRCA2 BRC motif may be exploited as an inhibitor of T. brucei growth, we ectopically expressed this peptide segment in the procyclic form of the parasite and evaluated its effects on cell survival as well as the sensitivity of these cells to the DNA damaging agent methyl methane sulfonate (MMS). Expression of a single BRC motif led to MMS sensitivity and inhibited cellular proliferation in T. brucei.     

重组人分泌型endostatin的纯化及其抑癌活性探讨

目的：纯化毕赤酵母菌GSll5株表达的分泌型人endostatin蛋白，并对其抑癌活性进行研究。方法：利用SepharoseG—25及Heparin亲和层析柱纯化重组蛋白，并以MTT法测定重组endostatin对人脐静脉血管内皮细胞(ECV-304)增殖的抑制活性；另以HepG2.2．15细胞注射裸鼠成瘤后，体内验证重组蛋白的抑瘤活性。结果：MTT结果显示纯化后的endostatin在体外可特异性抑制人脐静脉内皮细胞的增殖，最高抑制率为86．0％；动物实验证明其可明显抑制荷瘤动物肿瘤的生长。结论：经纯化后的重组endostatin具有较强抑癌活性，将为临床抗血管生成治疗实体瘤研究奠定基础。     

Mutagenic and Estrogenic Effects of Organic Compounds in Water Treated by Different Processes:A Pilot Study

Objective In this study, a pilot-scale investigation was conducted to examine and compare the biotoxicity of the organic compounds in effluents from five treatment processes (P1-P5) where each process was combination of preoxidation (O3), coagulation, sedimentation, sand filtration, ozonation, granular activated carbon, biological activated carbon and chlorination (NaClO).
Methods Organic compounds were extracted by XAD-2 resins and eluted with acetone and dichlormethane (DCM). The eluents were evaporated and redissolved with DMSO or DCM. The mutagenicity and estrogenicity of the extracts were assayed with the Ames test and yeast estrogen screen (YES assay), respectively. The organic compounds were detected by GC-MS.
Results The results indicated that the mutation ratio (MR) of organic compounds in source water was higher than that for treated water. GC-MS showed that more than 48 organic compounds were identified in all samples and that treated water had significantly fewer types and concentrations of organic compounds than source water.
Conclusion To different extents, all water treatment processes could reduce both the mutagenicity and estrogenicity, relative to source water. P2, P3, and P5 reduced mutagenicity more effectively, while P1 reduced estrogenicity, most effectively. Water treatment processes in this pilot plant had weak abilities to remove Di-n-butyl phthalate or 1, 2-Benzene dicarboxylic acid.     

Base excision repair of both uracil and oxidatively damaged bases contribute to thymidine deprivation-induced radiosensitization

PURPOSE: Increased cellular sensitivity to ionizing radiation due to thymidine depletion is the basis of radiosensitization with fluoropyrimidine and methotrexate. The mechanism responsible for cytotoxicity has not been fully elucidated but appears to involve both the introduction of uracil into, and its removal from, DNA. The role of base excision repair of uracil and oxidatively damaged bases in creating the increased radiosensitization during thymidine depletion is examined. METHODS AND MATERIALS: Isogenic strains of S. cerevisiae differing only at loci involved in DNA repair functions were exposed to aminopterin and sulfanilamide to induce thymidine deprivation. Cultures were irradiated and survival determined by clonogenic survival assay. RESULTS: Strains lacking uracil base excision repair (BER) activities demonstrated less radiosensitization than the parental strain. Mutant strains continued to show partial radiosensitization with aminopterin treatment. Mutants deficient in BER of both uracil and oxidatively damaged bases did not demonstrate radiosensitization. A recombination deficient rad52 mutant strain was markedly sensitive to radiation; addition of aminopterin increased radiosensitivity only slightly. Radiosensitization observed in rad52 mutants was also abolished by deletion of the APN1, NTG1, and NTG2 genes. CONCLUSION: These data suggest radiosensitization during thymidine depletion is the result of BER activities directed at both uracil and oxidatively damaged bases.