The impact of catalase expression on the replicative lifespan of Saccharomyces cerevisiae.

The role of catalase on Saccharomyces cerevisiae replicative lifespan was investigated using a wild-type haploid laboratory yeast W303a, a catalase A mutant, a catalase T mutant and an acatalasaemic mutant. Lifespan analysis was performed in two different environmental conditions. Under repressing conditions, on glucose media, catalase T activity, but not catalase A activity was necessary to assure longevity. However, under derepressing conditions, on ethanol media, both catalases were required for longevity assurance. Although catalase activity and carbon source influence yeast lifespan, the relationship between oxidative defence and replicative senescence is complex.     

红色荧光蛋白在酿酒酵母中的表达特性研究

目的研究红色荧光蛋白编码基因Dsred在酿酒酵母菌中的快速克隆与表达。方法根据已发表基因序列设计引物,采用连续重叠PCR方法快速克隆获得全长Dsred基因,将其与pMD-18T载体连接后进行测序鉴定。通过In-fusion方法将鉴定正确的pMD-Dsred重组载体与酿酒酵母表达载体pYeDP60进行连接,测序后利用LiAc方法将鉴定正确的pYeDP60-Dsred重组表达载体转化至酿酒酵母菌W303-1B中,PCR扩增筛选阳性克隆,获得的W303B[pYeDP60-Dsred]工程菌经诱导培养后进行SDS-PAGE电泳分析和绿光激发荧光成像检测。将工程菌分别接种至YPD、YPG、SCG和SCD培养基,培养48、72、96、120和144h后分别测定吸光度(A600)值。取诱导表达后的工程菌(菌液组)进行离心(菌体组)、离心后加甘油(高渗组)处理,分别置于–70、–20、4、28和37℃条件培养,荧光显微镜观察其表达特性。结果连续重叠PCR扩增和测序鉴定结果表明,扩增获得的Dsred基因长为678bp,其序列与已发表的基因序列完全一致;Dsred基因已成功插入pYeDP60-Dsred重组表达载体,且受酵母诱导型启动子GAL10-CYC1调控表达。PCR扩增筛选和SDS-PAGE分析显示,pYeDP60-Dsred重组表达载体已成功导入酿酒酵母菌中,诱导表达产物相对分子质量与预期相符,且诱导后工程菌可在绿光激发下发出红色荧光。4种培养基内工程菌的菌体生长情况无明显差别,重组Dsred红色荧光蛋白表达不会抑制酿酒酵母菌体生长。荧光显微镜观察显示,工程菌经不同处理后,高渗组红色荧光蛋白成熟时间最短,菌液组时间最长;红色荧光蛋白在37℃条件下培养时成熟最早,但降解速度较快。结论成功构建了pYeDP60-Dsred重组酿酒酵母表达载体,实现了Dsred基因在酿酒酵母菌体内的异源表达。红色荧光蛋白表达对酿酒酵母菌体生长无明显影响,且离心保留菌体和加入甘油等缺水高渗处理都有利于红色荧光蛋白的成熟。     

过氧化氢酶基因多态性与疾病相关性的研究

过氧化氢酶(catalase,CAT)是人体内很重要的一种抗氧化酶,它与超氧化物歧化酶(superoxide dismutase,SOD),谷胱甘肽过氧化物酶(glutathione peroxidase,GSH-Px)共同构成人体重要的抗氧化酶系统,三者协同,减少了活性氧自由基的产生,防止脂质过氧化及其中间代谢产物对机体的损害,维持体内氧化-抗氧化平衡.过氧化氢酶的基因多态性可能与该酶的活性及转录活性有关,从而影响个体间对疾病的易感性不同.     

Regulation of isoleucine-valine biosynthesis in Saccharomyces cerevisiae

Summary The threonine deaminase gene (ILV1) of Saccharomyces cerevisiae has been designated multifunctional since Bollon (1974) indicated its involvement both in the catalysis of the first step in isoleucine biosynthesis and in the regulation of the isoleucine-valine pathway. Its role in regulation is characterized by a decrease in the activity of the five isoleucine-valine enzymes when cells are grown in the presence of the three branched-chain amino acids, isoleucine, valine and leucine (multivalent repression). We have demonstrated that the regulation of AHA reductoisomerase (encoded by ILV5) and branched-chain amino acid transaminase is unaffected by the deletion of ILV1, subsequently revealing that the two enzymes can be regulated in the absence of threonine deaminase. Both threonine deaminase activity and ILV1 mRNA levels increase in mutants (gcd2 and gcd3) having constitutively derepressed levels of enzymes under the general control of amino acid biosynthesis, as well as in response to starvation for tryptophan and branched-chain amino acid imbalance. Thus, the ILV1 gene is under general amino acid control, as is the case for both the ILV5 and the transaminase gene. Multivalent repression of reductoisomerase and transaminase can be observed in mutants defective in general control (gcn and gcd), whereas this is not the case for threonine deaminase. Our analysis suggests that repression effected by general control is not complete in minimal medium. Amino acid dependent regulation of threonine deaminase is only through general control, while the branched-chain amino acid repression of AHA reducto isomerase and the transaminase is caused both by general control and an amino acid-specific regulation.     

人免疫缺陷病毒1(HIV-1)膜蛋白基因片段在酵母中的克隆表达

目的为获得足够量的膜糖蛋白,以便于对不同ＨＩＶ分离株膜糖蛋白的结构与功能进行进一步的研究。方法从人免疫缺陷病毒１（ＨＩＶ－１）ＨＸＢ２分离株原病毒基因组的重组质粒ｐＨＸＢ２中克隆了两段膜糖蛋白基因（ＥＮＶ）片段。以酵母穿梭诱导表达质粒ｐＹＥＳ２为载体,构建了两个相应的重组表达质粒ｐＹＥＮＶ１和ｐＹＥＮＶ２;进一步利用大肠杆菌β－半乳糖苷酶基因（β－ｌａｃＺ）构建了ＨＩＶ－１膜外糖蛋白ＤＮＡ片段与β－ｌａｃＺ基因的融合表达质粒。将此３种质粒分别转化单细胞真核生物酿酒酵母ＢＪ１９９１,得到的转化子经半乳糖诱导表达后进行菌体全蛋白的ＳＤＳ－ＰＡＧＥ分析。结果克隆的基因片段在酿酒酵母中产生了分子质量为５０×１０３的特异性诱导蛋白;对含此融合表达质粒的酵母转化子半乳糖诱导后表达产物的免疫检测表明,与对照菌株相比,融合表达产物具有和ＨＩＶ－１阳性血清抗体反应的抗原性。结论可通过β－半乳糖苷酶活性的测定直接指示抗原片段的表达;为表达的膜糖蛋白片段的进一步分离纯化打下了一定基础     

血管紧张素II通过细胞外信号调节激酶1/2通路调控过氧化氢酶的表达及促进成纤维细胞表型转化*

 目的： 探讨细胞外信号调节激酶1/2(ERK1/2)在高血压大鼠模型动脉外膜血管重塑中的作用。方法: 利用血管紧张素II (Ang II)微泵灌注制备高血压大鼠模型,随机分为未处理组、生理盐水灌注组和Ang II灌注组。分别检测各组大鼠尾动脉收缩压及血管形态学改变;Western blotting技术检测外膜成纤维细胞过氧化氢酶(CAT)蛋白在未处理组、单纯Ang II、ERK1/2抑制剂PD98059和Ang II+PD98059培养下的表达。结果: 大鼠颈动脉HE染色和收缩压结果显示,与未处理组及生理盐水灌注组相比,Ang II组大鼠颈动脉中膜厚度和收缩压明显增加(P<0.01),动脉形态结构有明显改变,并且有显著的病理性血管重塑发生。Western blotting检测结果显示,PD98059作用下CAT比单纯Ang II明显增高(P<0.05),表明ERK1/2信号通路能够恢复Ang II诱导的CAT表达下调。结论: Ang II可能通过ERK1/2信号通路下调血管外膜CAT的表达,进而促进血管细胞表型转化,导致血管病理性重塑发生。     

Phosphatidylglycerolphosphate synthase encoded by the PEL1/PGS1 gene in Saccharomyces cerevisiae is localized in mitochondria and its expression is regulated by phospholipid precursors

The PEL1/PGS1 gene of the yeast Saccharomyces cerevisiae is essential for the viability of rho ^–/rho° mutants and the normal cardiolipin content of cells. The PEL1-GFP fusion gene has been found to complement the pel1/pgs1 mutation and its fluorescent protein was localized to mitochondria similarly to the β-galactosidase activity of a protein encoded by the PEL1-lacZ fusion gene. The expression of the PEL1-lacZ reporter gene was repressed in cells grown in the presence of inositol and choline, reduced in the ino2 and ino4 strains, but constitutive in the opi1 null-mutant strain. The results demonstrate that Pel1p, playing a vital role in cells impaired in the mitochondrial DNA, is localized in the mitochondria and expressed in response to inositol and choline. Received: 15 June / 15 July 1998     

Quorum-sensing systems trigger catalase expression to reverse the oxyR deletion-mediated VBNC state in Salmonella typhimurium

OxyR is an important regulatory protein that plays a key role in anti-oxygenation, and its deletion causes a special VBNC (Viable But Non-Culturable) state in many bacteria including Salmonella typhimurium. The S. typhimurium in the VBNC state can grow in LB broth but cannot grow on an LB plate unless its concentration is sufficiently high. However, the mechanism that reverses this state is not clear. In this study, conditioned media containing autoinducer collected from the wild type strain can restore the growth of low concentrations of the oxyR mutant strain on LB plates, and S. typhimurium collected from the plate has higher catalase activity than that from the broth, suggesting that a quorum-sensing system can trigger catalase expression to resuscitate the organism from the VBNC state independent of the OxyR regulon. We discovered a novel catalase (STM14_2049, Cat) whose expression is strictly concentration-dependent. The purified Cat protein has obvious catalase activity in vitro and in vivo and can restore the growth of the low concentration oxyR mutant strain. Thus, we believed Cat plays a role in VBNC resuscitation process. By understanding this mechanism, we can further understand the antioxidation and quorum-sensing systems in Salmonella typhimurium.     

Wasting in adjuvant-induced arthritis and its relationship to plasma zinc,copper and liver metallothionein

The appearance of joint inflammation (JI) 14 days after the injection of adjuvant (AJ) in the tail of rats is associated with a cachectic syndrome which is characterised by marked weight loss (WL). The degree of weight loss was examined in relation to the extent of change in other markers of inflammation including increased plasma copper (pCu), decreased plasma zinc (pZn) and increased hepatic metallothionein (hMT). At 14 days post-AJ injection, arthritic rats showed the following changes, relative to the controls: body weight, 12% decrease, pZn, 50% decrease; pCu, 90% increase and hMT, 11-fold increase (allp<0.001). Significant relationships were observed between JI, WL, pZn and hMT. The following coefficients of determination (r ²) were observed; JI and WL,–0.530, JI and pZn,–0.485; JI and hMT, 0.286; WL and hMT, –0.510 (allp<0.007). There was a strong relationship between the decreased pZn and increased hMT;r ²=–0.456 (p<0.001). While increased pCu was clearly associated with AJ-arthritis in these rats, there was no quantitative relationship between the extent of change in pCu and the other parameters measured (r ² all<0.01). The highest correlation observed was between pZn and WL (r ²=0.637,p<0.001)., While the initial depression of pZn may be the result of increased hepatic hMT levels, longer term reductions in pZn levels are linked to systemic inflammation, the degree of arthritis and associated weight loss.     

Control of replication initiation and heterochromatin formation in Saccharomyces cerevisiae by a regulator of meiotic gene expression

Heterochromatinization at the silent mating-type loci HMR and HML in Saccharomyces cerevisiae is achieved by targeting the Sir complex to these regions via a set of anchor proteins that bind to the silencers. Here, we have identified a novel heterochromatin-targeting factor for HML, the protein Sum1, a repressor of meiotic genes during vegetative growth. Sum1 bound both in vitro and in vivo to HML via a functional element within the HML-E silencer, and sum1Delta caused HML derepression. Significantly, Sum1 was also required for origin activity of HML-E, demonstrating a role of Sum1 in replication initiation. In a genome-wide search for Sum1-regulated origins, we identified a set of autonomous replicative sequences (ARS elements) that bound both the origin recognition complex and Sum1. Full initiation activity of these origins required Sum1, and their origin activity was decreased upon removal of the Sum1-binding site. Thus, Sum1 constitutes a novel global regulator of replication initiation in yeast.