Expression of chicken beta-actin in Saccharomyces cerevisiae

Actin interacts with a number of so-called actin-binding proteins which participate at various stages of the cell motility process such as regulation of filament formation, assembly and disassembly of filaments, force generation and depolymerization. Gene technology makes a precise mapping of the interacting surfaces on the actin molecules possible by studying specifically designed actin mutants expressed in a suitable organism. In addition, the production of engineered actin will become increasingly important when the three-dimensional structure of actin is determined. Chicken beta-actin can be produced in large quantities in Escherichia coli but such actin shows only a limited biological activity and thus seems to be of minor interest in future studies of structure-function relationships of this molecule. To circumvent the problem of a denatured bacterial protein, the yeast Saccharomyces cerevisiae was chosen as an alternative organism to express actin. This paper describes the expression, isolation and characterization of the yeast-produced chicken beta-actin. From a 12-liter culture of yeast cells, 500 micrograms of polymerizable beta-actin was isolated.     

Enhanced peptide secretion by gene disruption of CYM1, a novel protease in Saccharomyces cerevisiae.

Saccharomyces cerevisiae is a widely used host in the production of therapeutic peptides and proteins. Here we report the identification of a novel endoprotease in S. cerevisiae. It is encoded by the CYM1 gene and is specific for the C-terminus of basic residues of heterologously expressed peptides. Gene disruption of CYM1 not only reduced the intracellular proteolysis, but also enhanced the secretion of heterologously expressed peptides such as growth hormone, pro-B-type natriuretic peptide and pro-cholecystokinin. Cym1p resembles metalloendoproteases of the pitrilysin family with the HXXEH(X)E(71-77) catalytic domain as seen in insulysin, nardilysin and human metalloprotease 1. It is a nuclear encoded protease that localizes to mitochondria without a hydrophobic N-terminal signal sequence or a C-terminal tail-anchor. The protease does not require post-translational processing prior to activation and it contains cytosolic activity that processes peptides designated for the secretory pathway prior to translocation into the endoplasmic reticulum.     

Improved method for the PCR-based gene disruption in Saccharomyces cerevisiae

The PCR-based gene disruption strategy originally devised by Baudin et al. is widely used for gene targeting in Saccharomyces cerevisiae. An advantage of this strategy is its simplicity in making targeting constructs. The efficiencies of the targeted disruption are highly variable from locus to locus, however, and often very low. In this report, a method for improving the gene deletion efficiency is described.     

Fructose bisphosphatase of Saccharomyces cerevisiae. Cloning, disruption and regulation of the FBP1 structural gene

Fructose bisphosphatase catalyzes a key reaction of gluconeogenesis. We have cloned the fructose bisphosphatase (FBP1) structural gene from Saccharomyces cerevisiae by screening a genomic library for complementation of an Escherichia coli fbp deletion mutation. The cloned DNA expresses in E. coli a fructose bisphosphatase activity which is precipitable with antibodies specific for the yeast enzyme and is sensitive to inhibition by fructose 2,6-bisphosphate. Evidence is presented demonstrating that the entire gene, including all cis-acting regulatory sequences, has been cloned. A substitution mutation that disrupts FBP1 was incorporated into the yeast genome by transplacement to construct a fructose bisphosphatase null mutation. The fbp1 mutant strain is a hexose auxotroph, otherwise growing normally. Southern blot hybridization analysis confirmed the structure of the transplacement and demonstrated that FBP1 is present in single copy in the haploid genome. Northern blot hybridization analysis revealed an mRNA of about 1350 nucleotides, whose presence was repressible by glucose in the medium. Fructose bisphosphatase activity was not greatly overproduced when the FBP1 gene was present on a multicopy vector in yeast.     

Nonsense mutations in the can1 locus of Saccharomyces cerevisiae.

Yeast mutants resistant to L-canavanine were selected. All were recessive and fell into the can1 complementation group. Nonsense mutations were identified among them by using a set of different suppressors. Frequencies of UAA, UAG, and presumed UGA mutations were 14.8, 0.8, and 0.4%, respectively. A high incidence of nonsense mutations having discriminatory suppression patterns was characteristic of the locus.     

Specificity of the mutator effect caused by disruption of the RAD1 excision repair gene of Saccharomyces cerevisiae.

Disruption of RAD1, a gene controlling excision repair in the yeast Saccharomyces cerevisiae, increased the frequency of spontaneous forward mutation in a plasmid-borne copy of the SUP4-o gene. To characterize this effect in detail, a collection of 249 SUP4-o mutations arising spontaneously in the rad1 strain was analyzed by DNA sequencing. The resulting mutational spectrum was compared with that derived from an examination of 322 spontaneous SUP4-o mutations selected in an isogenic wild-type (RAD1) strain. This comparison revealed that the rad1 mutator phenotype was associated with increases in the frequencies of single-base-pair substitution, single-base-pair deletion, and insertion of the yeast retrotransposon Ty. In the rad1 strain, the relative fractions of these events and their distributions within SUP4-o exhibited features similar to those for spontaneous mutagenesis in the isogenic RAD1 background. The increase in the frequency of Ty insertion argues that Ty transposition can be activated by unrepaired spontaneous DNA damage, which normally would be removed by excision repair. We discuss the possibilities that either translesion synthesis, a reduced fidelity of DNA replication, or a deficiency in mismatch correction might be responsible for the majority of single-base-pair events in the rad1 strain.     

Primary structure and disruption of the phosphatidylinositol synthase gene of Saccharomyces cerevisiae

The wild-type yeast nuclear gene, PIS, encodes phosphatidylinositol synthase (CDPdiacylglycerol-inositol 3-phosphatidyltransferase, EC 2.7.8.11) (Nikawa, J., and Yamashita, S. (1984) Eur. J. Biochem. 143, 251-256). We now report the sequence of the cloned 2, 129-base pair DNA and the location of the PIS coding region within the sequence. The PIS coding frame is capable of encoding 220 amino acid residues with a calculated molecular weight of 24,823. On Northern blot analysis, an RNA species that hybridized with the coding region was detected in the total poly(A)+ RNA of the wild-type yeast. The primary translation product contains a region showing local sequence homology with yeast phosphatidylserine synthase (EC 2.7.8.8) and Escherichia coli 3-phosphatidyl-1'-glycerol-3'-phosphate synthase (EC 2.7.8.5), suggesting that these three enzymes are evolutionarily related. The PIS gene was disrupted in vitro through insertion of the yeast HIS3 gene into the coding region. A heterozygous diploid, PIS/pis::HIS3, constructed from a PIS/PIS his3/his3 diploid by replacing one of the wild-type PIS genes with the disrupted PIS gene, showed no segregation of viable His+ spores on tetrad analysis, indicating that disruption of the PIS gene is lethal. The nonviable spores were in an arrested state with a characteristic terminal phenotype, suggesting that the function of the PIS gene is essential for progression of the yeast cell cycle.     

The ICL1 gene from Saccharomyces cerevisiae.

The glyoxylate cycle is essential for the utilization of C2 compounds by the yeast Saccharomyces cerevisiae. Within this cycle, isocitrate lyase catalyzes one of the key reactions. We obtained mutants lacking detectable isocitrate lyase activity, screening for their inability to grow on ethanol. Genetic and biochemical analysis suggested that they carried a defect in the structural gene, ICL1. The mutants were used for the isolation of this gene and it was located on a 3.1-kb BglII-SphI DNA fragment. We then constructed a deletion-substitution mutant in the haploid yeast genome. It did not have any isocitrate lyase activity and lacked the ability to grow on ethanol as the sole carbon source. Both strands of a DNA fragment carrying the gene and its flanking regions were sequenced. An open reading frame of 1671 bp was detected, encoding a protein of 557 amino acids with a calculated molecular mass of 62515 Da. The deduced amino acid sequence shows extensive similarities to genes encoding isocitrate lyases from various organisms. Two putative cAMP-dependent protein-kinase phosphorylation sites may explain the susceptibility of the enzyme to carbon catabolite inactivation.     

The Saccharomyces cerevisiae DPM1 gene encoding dolichol-phosphate-mannose synthase is able to complement a glycosylation-defective mammalian cell line.

The Saccharomyces cerevisiae DPM1 gene product, dolichol-phosphate-mannose (Dol-P-Man) synthase, is involved in the coupled processes of synthesis and membrane translocation of Dol-P-Man. Dol-P-Man is the lipid-linked sugar donor of the last four mannose residues that are added to the core oligosaccharide transferred to protein during N-linked glycosylation in the endoplasmic reticulum. We present evidence that the S. cerevisiae gene DPM1, when stably transfected into a mutant Chinese hamster ovary cell line, B4-2-1, is able to correct the glycosylation defect of the cells. Evidence for complementation includes (i) fluorescence-activated cell sorter analysis of differential lectin binding to cell surface glycoproteins, (ii) restoration of Dol-P-Man synthase enzymatic activity in crude cell lysates, (iii) isolation and high-performance liquid chromatography fractionation of the lipid-linked oligosaccharides synthesized in the transfected and control cell lines, and (iv) the restoration of endoglycosidase H sensitivity to the oligosaccharides transferred to a specific glycoprotein synthesized in the DPM1 CHO transfectants. Indirect immunofluorescence with a primary antibody directed against the DPM1 protein shows a reticular staining pattern of protein localization in transfected hamster and monkey cell lines.     

Identification and analysis of a DNA fragment from Saccharomyces kluyveri that can complement the loss of CDC25 function in Saccharomyces cerevisiae.

In the budding yeast, Saccharomyces cerevisiae, the function of wild-type Ras proteins is dependent on the CDC25 protein, which promotes the exchange of guanine nucleotides bound to Ras. To facilitate the identification of proteins which similarly regulate Ras function in higher eukaryotes, we have identified the CDC25 gene from another budding yeast, Saccharomyces kluyveri, by low-stringency hybridization to an S. cerevisiae CDC25 restriction fragment. This protein, SKCDC25, shares significant amino acid homology with CDC25, SCD25, and Ste6 of Schizosaccharomyces pombe in the C-terminal portion of the protein. The expression of SKCDC25 in a temperature-sensitive cdc25 strain of S. cerevisiae complements the loss of endogenous CDC25 activity. The identification of the highly conserved C-terminal sequences, which direct bona fide CDC25 activity within these proteins, will aid in the isolation of CDC25 genes from higher eukaryotes.     

Purification, gene cloning, and gene disruption of the transcription elongation factor S-II in Saccharomyces cerevisiae.

Saccharomyces cerevisiae S-II was purified to near homogeneity as a protein stimulating RNA polymerase II. Four of seven lysyl endopeptidase-digested fragments of S-II were located in the PPR2 sequence reported previously. Analysis of a genomic clone of S-II revealed that S-II and PPR2 are the same protein consisting of 309 amino acid residues, and frame shifts were found in the sequence of PPR2 gene reported previously. Yeast S-II and mouse S-II showed high similarity in their amino acid sequences, especially in their amino-terminal and carboxyl-terminal regions. A gene disruption experiment showed that an S-II null mutant was not lethal under usual growth conditions, indicating that S-II is not essential for the growth of yeast.     

Isolation of the ARO1 cluster gene of Saccharomyces cerevisiae.

The AROl cluster gene was isolated by complementation in Saccharomyces cerevisiae after transformation with a comprehensive yeast DNA library of BamHI restriction fragments inserted into the shuttle vector YEp13. Most of the transformants exhibited the expected episomal inheritance of the ARO+ phenotype; however, one stable transformant has been shown to be an integration of the AROl fragment and the vector YEp13 at the arol locus. The insert containing AROl is a 17.2-kilobase pair (kbp) BamHI fragment which complements both nonsense and missense alleles of arol. Subcloning by Sau3AI partial digestion further locates the AROl segment to a 6.2-kbp region. An autonomously replicating sequence (ars) was found on the 17.2-kbp fragment. Yeast arol mutants transformed with the AROl episome express 5 to 12 times the normal level of the five AROl enzyme activities and possess elevated amounts of the AROl protein. The yeast AROl fragment also complemented aroA, aroB, aroD, and aroE mutants of Escherichia coli. The expression of AROl in both S. cerevisiae and E. coli was independent of the orientation of the fragment with respect to the vector.     

Overexpression of a novel gene, Cms1, can rescue the growth arrest of a Saccharomyces cerevisiae mcm10 suppressor.

MCM10 protein is an essential replication factor involved in the initiation of DNA replication. A mcm10 mutant (mcm10-1) of budding yeast shows a growth arrest at 37 degrees C. In the present work, we have isolated a mcm10-1 suppressor strain, which grows at 37 degrees C. Interestingly, this mcm10-1 suppressor undergoes cell cycle arrest at 14 degrees C. A novel gene, YLR003c, is identified by high-copy complementation of this suppressor. We called it as Cms1 (Complementation of Mcm 10 Suppressor). Furthermore, the experiments of transformation show that cells of mcm10-1 suppressor with high-copy plasmid but not low-copy plasmid grow at 14 degrees C, indicating that overexpression of Cms1 can rescue the growth arrest of this mcm10 suppressor at non-permissive temperature. These results suggest that CMS1 protein may functionally interact with MCM10 protein and play a role in the regulation of DNA replication and cell cycle control.     

A positive regulatory sequence of the Saccharomyces cerevisiae ENO1 gene

ENO1-'lacZ fusions with various lengths of the ENO1 5'-flanking region were constructed on various types of yeast plasmid vectors. The fully expressed level of beta Gal directed by ENO1-'lacZ fusions differed depending on the type of vector, but on any type of vector, beta Gal activity was not greatly influenced by the carbon source in the medium. The 86-bp DNA region of ENO1 at position -487 to -402 upstream of the initiation codon, in which we had previously delimited the positive regulatory region of ENO1 (Uemura, H., Shiba, T., Paterson, M., Jigami, Y., & Tanaka, H. (1986) Gene 45, 67-75), exerted its function without requiring precise location with respect to the TATA box. The action of the positive regulatory region was not affected by its orientation. In addition, the substitution of the UASs of PHO5, encoding repressible acid phosphatase, with the regulatory region of ENO1 changed the expression of PHO5-'lacZ gene to constitutive, irrespective of the concentration of inorganic phosphate in the medium. Furthermore, the GCR1 gene cloned in a multicopy plasmid increased the expression of the ENO1-'lacZ fused genes.     

The Schizosaccharomyces pombe pla1 gene encodes a poly(A) polymerase and can functionally replace its Saccharomyces cerevisiae homologue.

We have isolated the poly(A) polymerase (PAP) encoding gene pla1 [for poly(A) polymerase] from the fission yeast Schizosaccharomyces pombe. Protein sequence alignments with other poly(A) polymerases reveal that pla1 is more closely related to Saccharomyces cerevisiae PAP than to bovine PAP. The two yeast poly(A) polymerases share significant sequence homology not only in the generally conserved N-terminal part but also in the C-terminus. Furthermore, pla1 rescues a S. cerevisiae PAP1 disruption mutant. An extract from the complemented strain is active in the specific in vitro polyadenylation assay. In contrast, recombinant PLA1 protein can not replace bovine PAP in the mammalian in vitro polyadenylation assay. These results indicate a high degree of conservation of the polyadenylation machinery among the evolutionary diverged budding and fission yeasts.