Human DNA2 is a mitochondrial nuclease/helicase for efficient processing of DNA replication and repair intermediates

DNA2, a helicase/nuclease family member, plays versatile roles in processing DNA intermediates during DNA replication and repair. Yeast Dna2 (yDna2) is essential in RNA primer removal during nuclear DNA replication and is important in repairing UV damage, base damage, and double-strand breaks. Our data demonstrate that, surprisingly, human DNA2 (hDNA2) does not localize to nuclei, as it lacks a nuclear localization signal equivalent to that present in yDna2. Instead, hDNA2 migrates to the mitochondria, interacts with mitochondrial DNA polymerase gamma, and significantly stimulates polymerase activity. We further demonstrate that hDNA2 and flap endonuclease 1 synergistically process intermediate 5' flap structures occurring in DNA replication and long-patch base excision repair (LP-BER) in mitochondria. Depletion of hDNA2 from a mitochondrial extract reduces its efficiency in RNA primer removal and LP-BER. Taken together, our studies illustrate an evolutionarily diversified role of hDNA2 in mitochondrial DNA replication and repair in a mammalian system.     

toxR基因作为荧光定量PCR靶基因设计TaqMan探针快速检测副溶血弧菌

以toxR基因为靶基因,通过优化反应条件建立了快速检测副溶血弧茵的TaqMan实时荧光PCR方法.特异性试验表明,该方法能选择性检测副溶血弧茵,而与金黄色葡萄球菌、沙门氏菌、单增李斯特杆菌等多种常见的食源性病原茵没有交叉反应:灵敏度试验表明,该方法最少可检测到25个拷贝的toxR基因重组质粒,对纯培养物和模拟食品样品直接检测的灵敏度分别为21 cfu/mL和210 cfu/g;重复性试验表明,同一样品于试验内及试验间的变异系数分别为0.9%和1.3%:所制作的标准曲线在2.5 × 101～2.5 × 106拷贝数之间有较好的线性关系,能对副溶血孤菌进行准确的定量分析.结果表明,本研究所建立的副溶血弧菌实时荧光PCR检测方法具有特异性好,灵敏度高、重复性好的特点,能进行定量检测,而且检测时间从核酸抽提到出实验结果仅需要3 h.是快速检测副溶血弧菌的有效手段.     

Conformation-activity relationship on novel 4-pyridylmethylthio derivatives with antiangiogenic activity

We found 4-pyridylmethylthio derivative 1 to be very effective in using antiangiogenesis activity to prevent proliferation of HUVECs (Human Umbilical Vein Endothelial Cells), which was induced by vascular endothelial growth factor (VEGF). Compound 1 was equally effective in inhibiting VEGF receptor2 tyrosine kinase (KDR, IC₅₀ = 26 nM). We deduced that the inhibition was the result of binding the catalytic domain of VEGF receptor2 tyrosine kinase in a similar fashion to both phthalazine derivative PTK787 2 and anthranylamide derivative AAL993 3. In this report, we will describe the conformational analyses, from ab initio MO calculation and X-ray crystallographic analyses, of compound 1 and the analogs, which include non-active 9, all in comparison with 2 and 3. The conformation–activity relationships suggest that a nonbonded intramolecular interaction between the sulfur and the carbonyl oxygen of 1 was very important in inhibiting KDR.     

Synthesis and biological evaluation of N-mercaptoacylproline and N-mercaptoacylthiazolidine-4-carboxylic acid derivatives as leukotriene A4 hydrolase inhibitors

We studied the synthetic modification of structurally similar N-mercaptoacyl-L-proline and (4R)-N-mercaptoacylthiazolidine-4-carboxylic acid to obtain potent leukotriene A(4) (LTA(4)) hydrolase inhibitors. An N-mercaptoacyl group, (2S)-3-mercapto-2-methylpropionyl group, was effective for both scaffolds. Additional introduction of a large substituent such as 4-isopropylbenzylthio (3f), 4-tert-butylbenzylthio (3l) or 4-cyclohexylbenzylthio group (3m) with (S)-configuration at the C(4) position of proline yielded much more potent LTA(4) hydrolase inhibitors (IC(50); 52, 31, and 34 nM, respectively) than captopril (IC(50); 630,000 nM).     

Microbial communities in oligotrophic Lake Toya,Japan

 The vertical distributions of planktonic bacteria, chroococcoid cyanobacteria, and heterotrophic nanoflagellates (HNF) were examined in Lake Toya, an oligotrophic lake located in Hokkaido, the northern island of Japan, at monthly intervals from May 1993 to May 1994. The abundances of bacteria, cyanobacteria, and HNF during the study period ranged from 10⁴ to 10⁵,10² to 10⁴, 10 to 10² cells ml⁻¹, respectively. The range of bacterial abundances was among the lowest previously reported from other oligotrophic lakes. The vertical distributions of both bacteria and cyanobacteria were influenced by thermal stratification: they were homogeneous throughout the water column during the circulation period (January to April) and heterogeneous during the period of stratification (June to November). During the period of stratification, the cyanobacterial abundance decreased toward the surface in the euphotic zone while the frequency of diving cells (FDC) increased, suggesting that grazing pressure was high near the surface. This hypothesis was supported by the relatively high abundance of HNF at the surface and the negative correlation between HNF and cyanobacterial abundances in the euphotic zone (r = −0.503, n = 33, P < 0.05). On the other hand, multiple regression analysis revealed that 52% of the variation in bacterial abundance in the stratified period can be explained by chlorophyll a concentration, water temperature, and HNF abundance (df = 3, 45; F = 16.2; P < 0.01), suggesting that both substrate limitation and grazing loss by HNF were important factors controlling bacterial abundance in the lake. Received: June 21, 2002 / Accepted: October 16, 2002 Present address: 5-2-2-18-805 Kikusui-motomachi, Shiroishi, Sapporo 003-0825, Japan Present address: School of Environmental Science, University of Shiga Prefecture, 2500 Hassaka-cho, Hikone 522-8533, Japan Tel. +81-749-28-8307; Fax +81-749-28-8463 e-mail: ban@ses.usp.ac.jp Acknowledgments We thank Dr. H. Ueda for encouraging this study and Mr. Haruna and the members of the Plankton Laboratory, Hokkaido University, for their help in sampling. We also thank two anonymous reviewers for their critical comments. Correspondence to:S. Ban     

Synthesis of novel 1,4-benzoxazin-3-one derivatives as inhibitors against tyrosine kinases

We designed and synthesized a novel 1,4-benzoxazin-3-one derivative 4 which would have inhibitory activities against tyrosine kinases. They could be synthesized easily from various carboxylic acids 10 and commercially available amines using TFP resin without purification. In this article, we will report the design and synthesis of a novel 1,4-benzoxazin-3-one chemical library 4 and the inhibitory activities against KDR and ABL which are closely related to chronic diseases such as cancer.     

Carnitine palmitoyltransferase IA polymorphism P479L is common in Greenland Inuit and is associated with elevated plasma apolipoprotein A-I

Carnitine palmitoyltransferase IA, encoded by CPT1A, is a key regulator of fatty acid metabolism. Previously, a loss-of-function mutation, namely, c.1436 C→T (p.P479L), was reported in CPT1A in the homozygous state in Canadian aboriginal male with presumed CPT1A deficiency. To determine the population frequency of this variant, we determined CPT1A p.P479L genotypes in 1111 Greenland Inuit. Associations between genotype and variation in plasma total cholesterol, triglycerides, LDL, HDL, apolipoprotein (apo) B, and apoA-I was also investigated. We found the L479 allele occurs at a high frequency in this sample (0.73), while it was completely absent in 285 nonaboriginal samples. This suggests that the original proband''s symptoms were not likely due to the CPT1A p.P479L mutation because it is very common in Inuit and because symptoms suggesting CPT1A deficiency have not been reported in any carrier subsequently studied. However, CPT1A p.P479L was associated with elevated plasma HDL and apoA-I levels. The association with increased levels of HDL and apoA-I suggest that the polymorphism might protect against atherosclerosis.     

The construction of a genetic linkage map of non-heading Chinese cabbage （Brassica campestris ssp. chinensis Makino）

Non-heading Chinese cabbage （Brassica carnpestris ssp. chinensis Makino） is one of the most important vegetables in eastern China. A genetic linkage map was constructed using 127 doubled haploid （DH） lines, and the DH population was derived from a commercial hybrid ＂Hanxiao＂ （lines SW-13 x L-118）. Out of the 614 polyrnorphic markers, 43.49% were not assigned to any of the linkage groups （LGs）. Chi-square tests showed that 42.67% markers were distorted from expected Mendelian segregation ratios, and the direction of distorted segregation was mainly toward the paternal parent L-118. After sequentially removing the markers that had an interval distance smaller than 1 cM from the upper marker, the overall quality of the linkage map was increased. Two hundred and sixty-eight molecular markers were mapped into 10 LGs, which were anchored to the corresponding chromosome of the B. rapa reference map based on com- mon simple sequence repeat （SSR） markers. The map covers 973.38 cM of the genome and the average interval distance between markers was 3.63 cM. The number of markers on each LG ranged from 18 （R08） to 64 （R07）, with an average interval distance within a single LG from 1.70 cM （R07） to 6.71 cM （R06）. Among these mapped markers, 169 were sequence-related amplified polymorphism （SRAP） molecular markers, 50 were SSR markers and 49 were random amplification polymorphic DNA （RAPD） markers. With further saturation to the LG9 the current map offers a genetic tool for loci analysis for important agronomic traits.