Expression of the FOX1 gene of Saccharomyces cerevisiae is regulated by carbon source,but not by the known glucose repression genes

We have investigated the regulation of expression of the FOX1 gene of Saccharomyces cerevisiae which encodes acyl-CoA oxidase, the first enzyme in the peroxisomal oxidation of fatty acids. We have found that the FOX1 steady state mRNA level is repressed by glucose, partially induced by ethanol (but not by raffinose) and fully induced by oleic acid as a carbon source. Glucose repression was observed even if cultures were grown to stationary phase; however, if the glucose supply was limited initially then partial induction of FOX1 mRNA occurred upon growth to high cell density. A variety of mutants are known to affect the glucose repression of many genes, including the FOX3 gene which encodes the thiolase activity in peroxisomal oxidation. However, upon examination none of these mutants showed de-repression of FOX1 expression. Similarly we investigated the role of two inducers of genes encoding peroxisomal enzymes (namely SNF1 and ADR1). No evidence was found to suggest that either of these plays a significant role in the induction of FOX1 mRNA levels. These observations indicate that the regulation of FOX1 is under the control of as yet unidentified genes involved in catabolite repression and suggest that the regulatory circuit influencing acyl CoA oxidase activity, and hence oxidation and peroxisome function, is significantly different than that which might have been assumed from other studies.     

Molecular cloning and genetic characterization of the Saccharomyces cerevisiae NGS1/MRE11 gene

The Saccharomyces cerevisiae ngs1-1 mutant was previously identified by its enhanced sensitivity to simple DNA-alkylating agents such as methyl methanesulfonate but not to UV. Molecular cloning and sequencing of NGS1 as a putative DNA-alkylation repair gene revealed that it is identical to MRE11, a gene that is involved in DNA recombinational repair. In order to investigate functional domains of the Mre11 protein, nucleotide-sequence alterations of a number of mre11 mutant alleles, including ngs1-1, mre11-1 (ts), mre11-2, mre11-3 and mre11-58, were determined. Most of these mutations map to the N-terminus of Mre11, emphasizing the importance of this highly conserved domain. The ngs1-1 and mre11-3 mutants carry nonsense mutations resulting in truncated proteins. Missense mutations were found in mre11-1 (ts), mre11-2 and mre11-58, of which mre11-2 and mre11-58 mapped to the conserved phosphoesterase domains, indicating the involvement of these motifs in the formation and/or processing of DNA double-strand breaks. Finally, mitotic-recombination assays show that the mre11Δ mutation enhances inter-chromosomal recombination but decreases the intra-chromosomal deletion frequency. In addition, MRE11 appears to play different roles during spontaneous and alkylation-induced homologous mitotic recombination. Received: 19 August / 18 September 1998     

Yme2p is a mediator of nucleoid structure and number in mitochondria of the yeast Saccharomyces cerevisiae

A large number of gene products have been identified that either directly or indirectly alter the inheritance of mitochondrial DNA. In yeast, we have used a unique genetic screen based on the transfer of DNA from mitochondria to nucleus to identify nuclear-encoded gene products that are targeted to mitochondria and impact the stable inheritance of mitochondrial DNA. A specific allele of one of these genes, yme2-4, prevents even the low wild-type rate of mitochondrial DNA transfer to the nucleus and imparts significant temperature-sensitive and respiratory-growth defects. Intra- and extragenic suppressors of the yme2-4 growth phenotypes were isolated and analysis of these interacting genes reveals that both YME2 and its suppressors influence the structure and number of mitochondrial nucleoids. The yme2-4 allele decreases the average number of mtDNA nucleoids found in cells and the sensitivity of DNA in toluene-treated mitochondria to digestion by DNA exonuclease, effects reversed by intra- and extragenic suppressors. The extragenic suppressor, a missense allele of ILV5, encodes an enzyme of the branched-chain amino acid biosynthetic pathway that is also a component of mitochondrial nucleoids. A null allele of ILV5 suppresses transfer of mitochondrial DNA to the nucleus and displays synthetic interactions with yme2-4.     

The expression of PHO92 is regulated by Gcr1, and Pho92 is involved in glucose metabolism in Saccharomyces cerevisiae

Ydr374c (Pho92) contains a YTH domain in its C-terminal region and is a human YTHDF2 homologue. Previously, we reported that Pho92 regulates phosphate metabolism by regulating PHO4 mRNA stability. In this study, we found that growth of the ?pho92 strain on SG media was slower than that of the wild type and that PHO92 expression was up-regulated by non-fermentable carbon sources, such as ethanol and glycerol, but not by fermentable carbon sources. Furthermore, two conserved Gcr1-binding regions were identified in the upstream, untranslated region of PHO92. Gcr1 is an important factor involved in the coordinated regulation of glycolytic gene expression. Mutation of two Gcr1-binding sites of the PHO92 upstream region resulted in a growth defect on SD media. Finally, mutagenesis of the Gcr1-binding sites of the PHO92 upstream region and deletion of GCR1 resulted in up-regulation of PHO92, and this resulted from inhibition of PHO4 mRNA degradation. Based on these results, we suggest that Gcr1 regulates the expression of PHO92, and Pho92 is involved in glucose metabolism.     

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     

Matricellular protein SPARC/osteonectin expression is regulated by DNA methylation in its core promoter region

Background : SPARC/osteonectin is an evolutionarily conserved matricellular protein that modulates cell–matrix interaction and cell function. In all vertebrates, SPARC is dynamically expressed during embryogenesis. However, the precise function of SPARC and the regulatory elements required for its expression in particular during early embryogenesis are largely unknown. Results : The present study was undertaken to explore the molecular mechanisms that regulate sparc gene expression by in vivo functional characterization of the sparc promoter and identification of possible putative regulatory elements that govern basal promoter activity. We report here transient expression analyses of eGFP expression from transgenic zebrafish containing a Sparc‐iTol2‐eGFP‐BAC and/or 7.25 kb‐sparc‐Tol2‐eGFP constructs. eGFP expression was specifically found in the notochord, otic vesicle, fin fold, intermediate cell mass, and olfactory placode of BAC and Tol2 transposon vectors injected embryos. Deletion analysis revealed that promoter activity resides in the unique 5′‐untranslated intronic region. Computer‐based analysis revealed a putative CpG island immediately proximal to the translation start site within the intron sequence. Global inhibition of methylation with 5‐Aza‐2‐deoxycytidine promoted sparc expression in association with decreasing CpG methylation. Conclusions : Taken together, these data identify a contributory role for DNA methylation in regulating sparc expression in zebrafish embryogenesis. Developmental Dynamics 244:693–702, 2015. © 2015 Wiley Periodicals, Inc.