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B Dujon

Publications and source records attributed to B Dujon.

At least 19 recordsLinked to original sources
PubMed2005

CYGD: the Comprehensive Yeast Genome Database.

The Comprehensive Yeast Genome Database (CYGD) compiles a comprehensive data resource for information on the cellular functions of the yeast Saccharomyces cerevisiae and related species, chosen as the best understood model organism for eukaryotes. The database serves as a common resource generated by a European consortium, going beyond the provision of sequence information and functional annotations on individual genes and proteins. In addition, it provides information on the physical and functional interactions among proteins as well as other genetic elements. These cellular networks include metabolic and regulatory pathways, signal transduction and transport processes as well as co-regulated gene clusters. As more yeast genomes are published, their annotation becomes greatly facilitated using S.cerevisiae as a reference. CYGD provides a way of exploring related genomes with the aid of the S.cerevisiae genome as a backbone and SIMAP, the Similarity Matrix of Proteins. The comprehensive resource is available under http://mips.gsf.de/genre/proj/yeast/.

Binding Sites↗
PubMed2001

Evolution of gene order in the genomes of two related yeast species.

Changes in gene order between the genomes of two related yeast species, Saccharomyces cerevisiae and Saccharomyces bayanus var. uvarum were studied. From the dataset of a previous low coverage sequencing of the S. bayanus var. uvarum genome, 35 different synteny breakpoints between neighboring genes and two cases of local gene inversion were characterized in detail. The number and the type of the chromosomal rearrangements that have led to these differences were identified. We show that evolution of gene order in the genomes of these two yeast species is driven mainly by gene duplication onto different chromosomes followed by differential loss of the repeated copies. In addition, local gene inversions also would result from a mechanism of gene duplication, but in an inverted orientation, followed by loss of the original copy. The identification of traces of anciently duplicated genes, called relics, show that the loss of duplicates is more frequently caused by the accumulation of numerous mutations in one of the two copies than by DNA deletion. Surprisingly, gross chromosomal rearrangements such as translocations have only a minor effect on gene order reshuffling as they account for <10% of the synteny breakpoints.

Chromosome Inversion↗
PubMed2001

Microsatellite typing as a new tool for identification of Saccharomyces cerevisiae strains.

Since Saccharomyces cerevisiae appears to be an emerging pathogen, there is a need for a valuable molecular marker able to distinguish among strains. In this work, we investigated the potential value of microsatellite length polymorphism with a panel of 91 isolates, including 41 clinical isolates, 14 laboratory strains, and 28 strains with industrial relevance. Testing seven polymorphic regions (five trinucleotide repeats and two dinucleotide repeats) in a subgroup of 58 unrelated strains identified a total of 69 alleles (6 to 13 per locus) giving 52 different patterns with a discriminatory power of 99.03%. We found a cluster of clinical isolates sharing their genotype with a bakery strain, suggesting a digestive colonization following ingestion of this strain with diet. With the exception of this cluster of isolates and isolates collected from the same patient or from patients treated with Saccharomyces boulardii, all clinical isolates gave different and unique patterns. The genotypes are stable, and the method is reproducible. The possibility to make the method portable is of great interest for further studies using this technique. This work shows the possibility to readily identify S. boulardii (a strain increasingly isolated from invasive infections) using a unique and specific microsatellite allele.

Bronchoalveolar Lavage Fluid↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 1. A set of yeast species for molecular evolution studies.

The identification of molecular evolutionary mechanisms in eukaryotes is approached by a comparative genomics study of a homogeneous group of species classified as Hemiascomycetes. This group includes Saccharomyces cerevisiae, the first eukaryotic genome entirely sequenced, back in 1996. A random sequencing analysis has been performed on 13 different species sharing a small genome size and a low frequency of introns. Detailed information is provided in the 20 following papers. Additional tables available on websites describe the ca. 20000 newly identified genes. This wealth of data, so far unique among eukaryotes, allowed us to examine the conservation of chromosome maps, to identify the 'yeast-specific' genes, and to review the distribution of gene families into functional classes. This project conducted by a network of seven French laboratories has been designated 'Génolevures'.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 3. Methods and strategies used for sequence analysis and annotation.

The primary analysis of the sequences for our Hemiascomycete random sequence tag (RST) project was performed using a combination of classical methods for sequence comparison and contig assembly, and of specifically written scripts and computer visualization routines. Comparisons were performed first against DNA and protein sequences from Saccharomyces cerevisiae, then against protein sequences from other completely sequenced organisms and, finally, against protein sequences from all other organisms. Blast alignments were individually inspected to help recognize genes within our random genomic sequences despite the fact that only parts of them were available. For each yeast species, validated alignments were used to infer the proper genetic code, to determine codon usage preferences and to calculate their degree of sequence divergence with S. cerevisiae. The quality of each genomic library was monitored from contig analysis of the DNA sequences. Annotated sequences were submitted to the EMBL database, and the general annotation tables produced served as a basis for our comparative description of the evolution, redundancy and function of the Hemiascomycete genomes described in other articles of this issue.

Amino Acid Sequence↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 4. The genome of Saccharomyces cerevisiae revisited.

Since its completion more than 4 years ago, the sequence of Saccharomyces cerevisiae has been extensively used and studied. The original sequence has received a few corrections, and the identification of genes has been completed, thanks in particular to transcriptome analyses and to specialized studies on introns, tRNA genes, transposons or multigene families. In order to undertake the extensive comparative sequence analysis of this program, we have entirely revisited the S. cerevisiae sequence using the same criteria for all 16 chromosomes and taking into account publicly available annotations for genes and elements that cannot be predicted. Comparison with the other yeast species of this program indicates the existence of 50 novel genes in segments previously considered as 'intergenic' and suggests extensions for 26 of the previously annotated genes.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 8. Zygosaccharomyces rouxii.

This paper reports the genomic analysis of strain CBS732 of Zygosaccharomyces rouxii, a homothallic diploid yeast. We explored the sequences of 4934 random sequencing tags of about 1 kb in size and compared them to the Saccharomyces cerevisiae gene products. Approximately 2250 nuclear genes, 57 tRNAs, the rDNA locus, the endogenous pSR1 plasmid and 15 mitochondrial genes were identified. According to 18S and 25S rRNA cladograms and to synteny analysis, Z. rouxii could be placed among the S. cerevisiae sensu lato yeasts.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 10. Kluyveromyces thermotolerans.

A genomic exploration of Kluyveromyces thermotolerans was performed by random sequence tag (RST) analysis. We sequenced 2653 RSTs corresponding to inserts sequenced from both ends. We performed a systematic comparison with a complete set of proteins from Saccharomyces cerevisiae, other completely sequenced genomes and SwissProt. We identified six mitochondrial genes and 1358-1496 nuclear genes by comparison with S. cerevisiae. In addition, 25 genes were identified by comparison with other organisms. This corresponds to about 24% of the estimated gene content of this organism. A lower level of conservation is observed with orthologues to genes of S. cerevisiae previously classified as orphans. Gene order was found to be conserved between S. cerevisiae and K. thermotolerans in 56.5% of studied cases.

Amino Acid Sequence↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 12. Kluyveromyces marxianus var. marxianus.

As part of the comparative genomics project 'GENOLEVURES', we studied the Kluyveromyces marxianus var. marxianus strain CBS712 using a partial random sequencing strategy. With a 0.2 x genome equivalent coverage, we identified ca. 1300 novel genes encoding proteins, some containing spliceosomal introns with consensus splice sites identical to those of Saccharomyces cerevisiae, 28 tRNA genes, the whole rDNA repeat, and retrotransposons of the Ty1/2 family of S. cerevisiae with diverged Long Terminal Repeats. Functional classification of the K. marxianus genes, as well as the analysis of the paralogous gene families revealed few differences with respect to S. cerevisiae. Only 42 K. marxianus identified genes are without detectable homolog in the baker's yeast. However, we identified several genetic rearrangements between these two yeast species.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 13. Pichia angusta.

As part of a comparative genomics project on 13 hemiascomycetous yeasts, the Pichia angusta type strain was studied using a partial random sequencing strategy. With coverage of 0.5 genome equivalents, about 2500 novel protein-coding genes were identified, probably corresponding to more than half of the P. angusta protein-coding genes, 6% of which do not have homologs in Saccharomyces cerevisiae. Some of them contain one or two introns, on average three times shorter than those in S. cerevisiae. We also identified 28 tRNA genes, a few retrotransposons similar to Ty5 of S. cerevisiae, solo long terminal repeats, the whole ribosomal DNA cluster, and segments of mitochondrial DNA. The P. angusta sequences were deposited in EMBL under the accession numbers AL430961 to AL436044.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 15. Pichia sorbitophila.

This paper reports the genomic analysis of the strain CBS7064 of Pichia sorbitophila, a homothallic diploid yeast. We sequenced 4829 random sequence tags of about 1 kb and compared them to the Saccharomyces cerevisiae gene products. Approximately 1300 nuclear genes, 22 tRNAs, the rDNA locus, and six mitochondrial genes have been identified. The analysis of the rDNA genes has permitted to classify this organism close to the Candida species. Accession numbers from AL414896 to AL419724 at EMBL databank.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 16. Candida tropicalis.

The genome of the diploid hemiascomycetous yeast Candida tropicalis, an opportunistic human pathogen and an important organism for industrial applications, was explored by the analysis of 2541 Random Sequenced Tags (RSTs) covering about 20% of its genome. Comparison of these sequences with Saccharomyces cerevisiae and other species permitted the identification and the analysis of a total of more than 1000 novel genetic elements of C. tropicalis. Moreover, the present study confirms that in C. tropicalis, the rare CUG codon is read as a serine and not a leucine. The sequences have been deposited at EMBL with the accession numbers AL438875-AL441602.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 18. Comparative analysis of chromosome maps and synteny with Saccharomyces cerevisiae.

We have analyzed the evolution of chromosome maps of Hemiascomycetes by comparing gene order and orientation of the 13 yeast species partially sequenced in this program with the genome map of Saccharomyces cerevisiae. From the analysis of nearly 8000 situations in which two distinct genes having homologs in S. cerevisiae could be identified on the sequenced inserts of another yeast species, we have quantified the loss of synteny, the frequency of single gene deletion and the occurrence of gene inversion. Traces of ancestral duplications in the genome of S. cerevisiae could be identified from the comparison with the other species that do not entirely coincide with those identified from the comparison of S. cerevisiae with itself. From such duplications and from the correlation observed between gene inversion and loss of synteny, a model is proposed for the molecular evolution of Hemiascomycetes. This model, which can possibly be extended to other eukaryotes, is based on the reiteration of events of duplication of chromosome segments, creating transient merodiploids that are subsequently resolved by single gene deletion events.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 19. Ascomycetes-specific genes.

Comparisons of the 6213 predicted Saccharomyces cerevisiae open reading frame (ORF) products with sequences from organisms of other biological phyla differentiate genes commonly conserved in evolution from 'maverick' genes which have no homologue in phyla other than the Ascomycetes. We show that a majority of the 'maverick' genes have homologues among other yeast species and thus define a set of 1892 genes that, from sequence comparisons, appear 'Ascomycetes-specific'. We estimate, retrospectively, that the S. cerevisiae genome contains 5651 actual protein-coding genes, 50 of which were identified for the first time in this work, and that the present public databases contain 612 predicted ORFs that are not real genes. Interestingly, the sequences of the 'Ascomycetes-specific' genes tend to diverge more rapidly in evolution than that of other genes. Half of the 'Ascomycetes-specific' genes are functionally characterized in S. cerevisiae, and a few functional categories are over-represented in them.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 20. Evolution of gene redundancy compared to Saccharomyces cerevisiae.

We have evaluated the degree of gene redundancy in the nuclear genomes of 13 hemiascomycetous yeast species. Saccharomyces cerevisiae singletons and gene families appear generally conserved in these species as singletons and families of similar size, respectively. Variations of the number of homologues with respect to that expected affect from 7 to less than 24% of each genome. Since S. cerevisiae homologues represent the majority of the genes identified in the genomes studied, the overall degree of gene redundancy seems conserved across all species. This is best explained by a dynamic equilibrium resulting from numerous events of gene duplication and deletion rather than by a massive duplication event occurring in some lineages and not in others.

Ascomycota↗
PubMed2000

Genomic exploration of the hemiascomycetous yeasts: 21. Comparative functional classification of genes.

We explored the biological diversity of hemiascomycetous yeasts using a set of 22000 newly identified genes in 13 species through BLASTX searches. Genes without clear homologue in Saccharomyces cerevisiae appeared to be conserved in several species, suggesting that they were recently lost by S. cerevisiae. They often identified well-known species-specific traits. Cases of gene acquisition through horizontal transfer appeared to occur very rarely if at all. All identified genes were ascribed to functional classes. Functional classes were differently represented among species. Species classification by functional clustering roughly paralleled rDNA phylogeny. Unequal distribution of rapidly evolving, ascomycete-specific, genes among species and functions was shown to contribute strongly to this clustering. A few cases of gene family amplification were documented, but no general correlation could be observed between functional differentiation of yeast species and variations of gene family sizes. Yeast biological diversity seems thus to result from limited species-specific gene losses or duplications, and for a large part from rapid evolution of genes and regulatory factors dedicated to specific functions.

Ascomycota↗
PubMed2000

Transcriptional regulation of the Saccharomyces cerevisiae DAL5 gene family and identification of the high affinity nicotinic acid permease TNA1 (YGR260w).

We have studied the transcript levels of YGR260w and YLR004c, two genes encoding members of the yeast Dal5p subfamily of the major facilitator family, and we show that they increase when extracellular nicotinic acid and thiamine, respectively, are absent. The deletion of YGR260w in a bna1 auxotrophic mutant for nicotinic acid prevents growth at low nicotinic acid concentration. This suggests that YGR260w is necessary for nicotinic acid import into the cell. The direct measurement of nicotinic acid uptake on whole cells demonstrates that YGR260w encodes the yeast high affinity nicotinic acid permease. Its apparent K(m) of 1.7 microM is low enough to allow the uptake of the low concentrations of nicotinic acid normally secreted by wild type cells.

Base Sequence↗