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H Bussey

Publications and source records attributed to H Bussey.

At least 37 records · Page 2Linked to original sources
PubMed1998

Depolarization of the actin cytoskeleton is a specific phenotype in Saccharomyces cerevisiae.

The yeast actin cytoskeleton is polarized during most of the cell cycle. Certain environmental factors and mutations are associated with depolarization of the actin cytoskeleton. Is depolarization of the actin cytoskeleton a specific response, or is it a nonspecific reaction to harsh conditions or poor metabolism? If depolarization is a nonspecific response, then any mutation that slows growth should induce depolarization. In addition, the number of genes with the depolarization phenotype should constitute a relatively large part of the genome. To address this question, we determined the effect of slow growth on the actin cytoskeleton, and we determined the frequency of mutations that affect the actin cytoskeleton. Eight mutants with slow growth showed no defect in actin polarization, indicating that slow growth alone is not sufficient to cause depolarization. Among 273 viable haploids disrupted for ORFs of chromosome I and VIII and 950 viable haploids with random genome disruptions, none had depolarization of the cytoskeleton. We conclude that depolarization of the actin cytoskeleton is a specific phenotype.

Actins↗
PubMed1997

The Ktr1p, Ktr3p, and Kre2p/Mnt1p mannosyltransferases participate in the elaboration of yeast O- and N-linked carbohydrate chains.

We have determined a role for Ktr1p and Ktr3p as mannosyltransferases in the synthesis of the carbohydrate chains attached to Saccharomyces cerevisiae O- and N-modified proteins. KTR1 and KTR3 encode related proteins that are highly similar to the Kre2p/Mnt1p Golgi alpha1,2-mannosyltransferase (Lussier, M., Camirand, A., Sdicu, A.-M., and Bussey, H. (1993) Yeast 9, 1057-1063; Mallet, L., Bussereau, F., and Jacquet, M. (1994) Yeast 10, 819-831). Examination of the electrophoretic mobility of a specifically O-linked protein from mutants and an analysis of their total O-linked mannosyl chains demonstrates that Ktr1p, Ktr3p, and Kre2p/Mnt1p have overlapping roles and collectively add most of the second and the third alpha1,2-linked mannose residues on O-linked oligosaccharides. Determination of the mobility of the specifically N-linked glycoprotein invertase in different null strains indicates that Ktr1p, Ktr3p, and Kre2p are also jointly involved in N-linked glycosylation, possibly in establishing some of the outer chain alpha1,2-linkages.

Glycosylation↗
PubMed1997

The nucleotide sequence of Saccharomyces cerevisiae chromosome XVI.

The nucleotide sequence of the 948,061 base pairs of chromosome XVI has been determined, completing the sequence of the yeast genome. Chromosome XVI was the last yeast chromosome identified, and some of the genes mapped early to it, such as GAL4, PEP4 and RAD1 (ref. 2) have played important roles in the development of yeast biology. The architecture of this final chromosome seems to be typical of the large yeast chromosomes, and shows large duplications with other yeast chromosomes. Chromosome XVI contains 487 potential protein-encoding genes, 17 tRNA genes and two small nuclear RNA genes; 27% of the genes have significant similarities to human gene products, and 48% are new and of unknown biological function. Systematic efforts to explore gene function have begun.

Base Sequence↗
PubMed1997

Completion of the Saccharomyces cerevisiae genome sequence allows identification of KTR5, KTR6 and KTR7 and definition of the nine-membered KRE2/MNT1 mannosyltransferase gene family in this organism.

The KRE2/MNT1 mannosyltransferase gene family of Saccharomyces cerevisiae currently consists of the KRE2, YUR1, KTR1, KTR2, KTR3 and KTR4 genes. All six encode putative type II membrane proteins with a short cytoplasmic N-terminus, a membrane-spanning region and a highly conserved catalytic lumenal domain. Here we report the identification of the three remaining members of this family in the yeast genome. KTR5 corresponds to an open reading frame (ORF) of the left arm of chromosome XIV, and KTR6 and KTR7 to ORFs on the left arms of chromosomes XVI and IX respectively. The KTR5, KTR6 and KTR7 gene products are highly similar to the Kre2p/Mnt1p family members. Initial functional characterization revealed that some mutant yeast strains containing null copies of these genes displayed cell wall phenotypes. None was K1 killer toxin resistant but ktr6 and ktr7 null mutants were found to be hypersensitive and resistant, respectively, to the drug Calcofluor White.

Amino Acid Sequence↗
PubMed1997

Structural and functional conservation of the Caenorhabditis elegans timing gene clk-1.

Mutations in the Caenorhabditis elegans gene clk-1 affect biological timing and extend longevity. The gene clk-1 was identified, and the cloned gene complemented the clk-1 phenotypes and restored normal longevity. The CLK-1 protein was found to be conserved among eukaryotes, including humans, and structurally similar to the yeast metabolic regulator Cat5p (also called Coq7p). These proteins contain a tandem duplication of a core 82-residue domain. clk-1 complemented the phenotype of cat5/coq7 null mutants, demonstrating that clk-1 and CAT5/COQ7 share biochemical function and that clk-1 acts at the level of cellular physiology.

Amino Acid Sequence↗
PubMed1997

Ktr1p is an alpha-1,2-mannosyltransferase of Saccharomyces cerevisiae. Comparison of the enzymic properties of soluble recombinant Ktr1p and Kre2p/Mnt1p produced in Pichia pastoris.

The yeast genome contains a KRE2/MNT1 family of nine related genes with amino acid similarity to the alpha 1,2-mannosyltransferase Kre2p/Mnt1p, the only member of this family whose enzymic properties have been studied. In this study, the enzymic properties of Ktr1p, another member of this family, were studied and compared to those of Kre2p/Mnt1p. Recombinant soluble forms of Kre2p/Mnt1p and Ktr1p lacking their N-terminal regions were expressed as secreted proteins from the methylotrophic yeast Pichia pastoris. After induction with methanol, the medium contained approx, 40 and 400 mg/l of soluble recombinant Kre2p/Mnt1p and Ktr1p respectively. Both recombinant proteins were shown to exhibit alpha 1,2-mannosyltransferase activity. The enzymes have an absolute requirement for Mn2+ and a similar K(m) for mannose (280-350 mM), methyl-alpha-mannoside (60-90 mM) and GDP-mannose (50-90 microM), but the Vmax was approx. 10 times higher for Kre2p/Mnt1p than for Ktr1p. The enzymes have similar substrate specificities and utilize mannose, methyl-alpha-mannoside, alpha-1,2-mannobiose and methyl-alpha-1,2-mannobiose, as well as Man15-30GlcNAc, derived from mnn2 mutant glycoproteins, as substrates. The enzymes do not utilize alpha-1,6-mannobiose, alpha-1,6-mannotriose, alpha-1,6-mannotetraose, mammalian Man9GlcNAc or yeast Man9-10GlcNAc. These results indicate that Kre2p/ Mnt1p and Ktr1p are capable of participating in both N-glycan and O-glycan biosynthesis.

Amino Acid Sequence↗
PubMed1997

Histone H1 in Saccharomyces cerevisiae.

The existence of histone H1 in the yeast, Saccharomyces cerevisiae, has long been debated. In this report we describe the presence of histone H1 in yeast. YPL127c, a gene encoding a protein with a high degree of similarity to histone H1 from other species was sequenced as part of the contribution of the Montreal Yeast Genome Sequencing Group to chromosome XVI. To reflect this similarity, the gene designation has been changed HHO1 (Histone H One). The HHO1 gene is highly expressed as poly A+ RNA in yeast. Although deletion of this gene had no detectable effect on cell growth, viability or mating, it significantly altered the expression of beta-galactosidase from a CYC1-lacZ reporter. Fluorescence observed in cells expressing a histone H1-GFP protein fusion indicated that histone H1 is localized to the nucleus.

Amino Acid Sequence↗
PubMed1997

Molecular cloning of chromosome I DNA from Saccharomyces cerevisiae: characterization of the 54 kb right terminal CDC15-FLO1-PHO11 region.

Gene density near the ends of Saccharomyces cerevisiae chromosomes is much lower than on the rest of the chromosome. Non-functional gene-fragments are common and a high proportion of the sequences are repeated elsewhere in the genome. This sequence arrangement suggests that the ends of chromosomes play a structural rather than a coding role and may be analogous to the highly repeated heterochromatic DNA of higher organisms. In order to evaluate the function of the ends of S. cerevisiae chromosomes, the rightmost 54-kb of DNA from chromosome I was investigated. The region contains 16 open reading frames (ORFs) and two tRNA genes. Gene-disruption studies indicated that none of these genes are essential for growth on rich or minimal medium, mating or sporulation. In contrast to the central region where 80% of the genes are transcribed when cells are grown on rich medium, only seven ORFs and the two tRNA genes appeared to produce transcripts. Six of the transcribed ORFs were from the centromere-proximal part of the region, leaving the rightmost 35-kb with only a single sequence that is transcribed during vegetative growth. Two genes located 3 and 10-kb from the chromosome I telomere are almost identical to two genes located somewhat further from the chromosome VIII telomere. Surprisingly, the chromosome VIII copies were transcribed while the chromosome I genes were not. These results suggest that the chromosome I genes may be repressed by a natural telomere position effect. The low level of transcription, absence of essential genes as well as the repetitive nature of these sequences are consistent with their having a structural role in chromosome function.

Cell Cycle Proteins↗
PubMed1997

The ALD6 gene of Saccharomyces cerevisiae encodes a cytosolic, Mg(2+)-activated acetaldehyde dehydrogenase.

The deduced translation product of an open reading frame on the left arm of chromosome XVI of Saccharomyces cerevisiae, with the systematic name of YPL061w, is 500 amino acids in length and shares significant homology with aldehyde dehydrogenases. Amino acids 2 to 16 of the protein encoded by YPL061w were found to be identical to the N-terminal 15 amino acids of the purified cytosolic, Mg(2+)-activated acetaldehyde dehydrogenase (ACDH) of S. cerevisiae. This enzyme is thought to be involved in the production of acetate from which cytosolic acetyl-CoA is then synthesized. Deletion of YPL061w was detrimental to the growth of haploid strains of yeast; an analysis of one deletion mutant revealed a maximum specific growth rate (in complex medium containing glucose) of one-third of that displayed by the wild-type strain. Mutants deleted in YPL061w were also unable to use ethanol as a carbon source. As expected, the cytosolic, Mg(2+)-activated ACDH activity had been lost from the mutants, although the mitochondrial, K(+)-activated ACDH was readily detected.

Aldehyde Oxidoreductases↗
PubMed1997

Functional analysis of a 38 kilobase region on chromosome XVI in Saccharomyces cerevisiae.

In this report we assess the functional importance of 16 open reading frames (ORFs) contained within a 38 780 base-pair region immediately adjacent to the centromere on the right arm of chromosome XVI in Saccharomyces cerevisiae. This analysis involved replacing one copy of each ORF in a diploid strain with a cassette encoding the green fluorescent protein from the jellyfish Aequorea victoria and HIS3. Each replacement cassette was generated by PCR using oligonucleotide pairs with 45-base extensions complementary to sequences immediately upstream and downstream of the target gene's coding region. After replacement of the targeted genes, each gene-replacement strain was subjected to a series of genetic and phenotypic tests to assess the functional importance of the deleted gene. This analysis showed that two ORFs were essential, one for spores to germinate and another for vegetative growth. A third gene encoded a copper-fist-like transcription factor that was required for proper bud-site selection. One of the 16 ORFs was duplicated, a situation not observed in the strain used to sequence the yeast genome (S288C). RNA analysis showed 11 of the 16 ORFs in this region expressed steady-state poly(A+) RNA levels that were greater than or equal to 2% of the level expressed from the yeast actin gene, ACT1.

Blotting, Northern↗
PubMed1997

Large scale identification of genes involved in cell surface biosynthesis and architecture in Saccharomyces cerevisiae.

The sequenced yeast genome offers a unique resource for the analysis of eukaryotic cell function and enables genome-wide screens for genes involved in cellular processes. We have identified genes involved in cell surface assembly by screening transposon-mutagenized cells for altered sensitivity to calcofluor white, followed by supplementary screens to further characterize mutant phenotypes. The mutated genes were directly retrieved from genomic DNA and then matched uniquely to a gene in the yeast genome database. Eighty-two genes with apparent perturbation of the cell surface were identified, with mutations in 65 of them displaying at least one further cell surface phenotype in addition to their modified sensitivity to calcofluor. Fifty of these genes were previously known, 17 encoded proteins whose function could be anticipated through sequence homology or previously recognized phenotypes and 15 genes had no previously known phenotype.

Cell Membrane↗
PubMed1997

The yeast CWH41 gene encodes glucosidase I.

N-Glycosylation in the yeast Saccharomyces cerevisiae entails the synthesis of a Glc3Man9GlcNAc2 oligosaccharide precursor which is subsequently transferred to suitable protein acceptors, a process which is conserved among all eukaryotes. Processing of the oligosaccharide occurs immediately following this transfer, the first step being the removal of the terminal alpha-1,2-linked glucose by glucosidase I in the endoplasmic reticulum. Although yeast glucosidase I has been isolated, the yeast gene encoding this enzyme has not yet been identified. In the present work, it is shown that Cwh41p, a yeast endoplasmic reticulum protein previously identified as being required for normal cell wall beta-1,6-glucan synthesis (Jiang, Sheraton, Ram, Dijkgraaf, Klis, and Bussey (1996) J. Bacteriol., 178, 1162-1171), has significant amino acid similarity to the product of the human glucosidase I cDNA. Tetrad analysis for glucosidase I activity in vitro and in vivo was done on the progeny from the spores obtained from the heterozygous diploid, cwh41 delta::HIS3. It is shown that, unlike CWH41 cells, cell extracts obtained from cwh41 delta null mutants are unable to release glucose residues from the synthetic trisaccharide substrate alpha-D-Glc 1-->2 alpha-D-Glc 1-->3 alpha-D-Glc-O(CH2)8 COOCH3 in vitro. Following 1 h labeling of cells with [3H]mannose, analysis by high pressure liquid chromatography of the labeled N-linked oligosaccharides, combined with treatment with jack bean alpha mannosidase and yeast glucosidase I, shows that the oligosaccharides isolated form a cwh41 delta null mutant are fully glucosylated, retaining the three terminal glucose residues, whereas the oligosaccharides from CWH41 cells do not have any glucose residues. These results showing a lack of glucosidase I activity in cwh41 delta null mutants both in vitro and in vivo are consistent with the structural evidence that CWH41 encodes the yeast glucosidase I.

Amino Acid Sequence↗
PubMed1997

Analysis of a 103 kbp cluster homology region from the left end of Saccharomyces cerevisiae chromosome I.

The DNA sequence and preliminary functional analysis of a 103-kbp section of the left arm of yeast chromosome I is presented. This region, from the left telomere to the LTE1 gene, can be divided into two distinct portions. One portion, the telomeric 29 kbp, has a very low gene density (only five potential genes and 21 kbp of noncoding sequence), does not encode any "functionally important" genes, and is rich in sequences repeated several times within the yeast genome. The other portion, with 37 genes and only 14.5 kbp of noncoding sequence, is gene rich and codes for at least 16 "functionally important" genes. The entire gene-rich portion is apparently duplicated on chromosome XV as an extensive region of partial gene synteney called a cluster homology region. A function can be assigned with varying degrees of precision to 23 of the 42 potential genes in this region; however, the precise function is know for only eight genes. Nineteen genes encode products presently novel to yeast, although five of these have homologs elsewhere in the yeast genome.

Base Sequence↗
PubMed1996

Life with 6000 genes.

The genome of the yeast Saccharomyces cerevisiae has been completely sequenced through a worldwide collaboration. The sequence of 12,068 kilobases defines 5885 potential protein-encoding genes, approximately 140 genes specifying ribosomal RNA, 40 genes for small nuclear RNA molecules, and 275 transfer RNA genes. In addition, the complete sequence provides information about the higher order organization of yeast's 16 chromosomes and allows some insight into their evolutionary history. The genome shows a considerable amount of apparent genetic redundancy, and one of the major problems to be tackled during the next stage of the yeast genome project is to elucidate the biological functions of all of these genes.

Amino Acid Sequence↗
PubMed1996

The KNH1 gene of Saccharomyces cerevisiae is a functional homolog of KRE9.

The KNH1 gene from Saccharomyces cerevisiae was identified as an open reading frame on the right arm of chromosome IV. The product encoded by the KNH1 gene, Knhlp, shares 46% overall identity with Kre9p, a protein required for cell surface beta 1,6-glucan synthesis. While disruption of the KNH1 locus had no effect on cell growth, killer toxin sensitivity or beta 1,6-glucan levels, overexpression of KNH1 was found to suppress the severe growth defect of a kre9 delta mutant and restored the level of alkali-insoluble beta 1,6-glucan to almost wild-type levels. Knhlp, like Kre9p, can be found in the extracellular culture medium as an O-glycoprotein, with a molecular mass of 45-61 kDa. Disruption of both KNH1 and KRE9 is lethal, and unlike single kre9 delta mutants, could not be rescued by overproducing SKN7, a putative transcription factor involved in the regulation of extracellular matrix assembly. Transcription of KNH1 was found to be carbon-source and kre9 delta dependent, but SKN7 independent, suggesting that KNH1 is subject to alternative transcriptional control.

Amino Acid Sequence↗