Life with 6000 genes.
ABSTRACT 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.
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ABSTRACT: The Saccharomyces cerevisiae 14-spanner Drug:H+ Antiporter family 2 (DHA2) are transporters of the Major Facilitator Superfamily (MFS) involved in multidrug resistance (MDR). Although poorly characterized, DHA2 family members were found to participate in the export of structurally and functionally unrelated compounds or in the uptake of amino acids into the vacuole or the cell. In S. cerevisiae, the four ARN/SIT family members encode siderophore transporters and the two GEX family members encode glutathione extrusion pumps. The evolutionary history of DHA2, ARN and GEX genes, encoding 14-spanner MFS transporters, is reconstructed in this study. The translated ORFs of 31 strains from 25 hemiascomycetous species, including 10 pathogenic Candida species, were compared using a local sequence similarity algorithm. The constraining and traversing of a network representing the pairwise similarity data gathered 355 full size proteins and retrieved ARN and GEX family members together with DHA2 transporters, suggesting the existence of a close phylogenetic relationship among these 14-spanner major facilitators. Gene neighbourhood analysis was combined with tree construction methodologies to reconstruct their evolutionary history and 7 DHA2 gene lineages, 5 ARN gene lineages, and 1 GEX gene lineage, were identified. The S. cerevisiae DHA2 proteins Sge1, Azr1, Vba3 and Vba5 co-clustered in a large phylogenetic branch, the ATR1 and YMR279C genes were proposed to be paralogs formed during the Whole Genome Duplication (WGD) whereas the closely related ORF YOR378W resides in its own lineage. Homologs of S. cerevisiae DHA2 vacuolar proteins Vba1, Vba2 and Vba4 occur widespread in the Hemiascomycetes. Arn1/Arn2 homologs were only found in species belonging to the Saccharomyces complex and are more abundant in the pre-WGD species. Arn4 homologs were only found in sub-telomeric regions of species belonging to the Sacharomyces sensu strictu group (SSSG). Arn3 type siderophore transporters are abundant in the Hemiascomycetes and form an ancient gene lineage extending to the filamentous fungi. The evolutionary history of DHA2, ARN and GEX genes was reconstructed and a common evolutionary root shared by the encoded proteins is hypothesized. A new protein family, denominated DAG, is proposed to span these three phylogenetic subfamilies of 14-spanner MFS transporters.BMC Genomics 12/2013; 14(1):901. · 4.40 Impact Factor
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ABSTRACT: In this study, we systematically identify Old Yellow Enzymes (OYEs) from a diverse range of economically important fungi representing different ecology and lifestyle. Using active site residues and sequence alignments, we present a classification for these proteins into three distinct classes including a novel class (Class III) and assign names to sequences. Our in-depth phylogenetic analysis suggests a complex history of lineage-specific expansion and contraction for the OYE gene family in fungi. Comparative analyses reveal remarkable diversity in the number and classes of OYE among fungi. Quantitative real-time PCR (qRT-PCR) of Ascochyta rabiei OYEs indicates differential expression of OYE genes during oxidative stress and plant infection. This study shows relationship of OYE with fungal ecology and lifestyle, and provides a foundation for future functional analysis and characterization of OYE gene family.Scientific Reports 01/2014; 4:4013. · 2.93 Impact Factor
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ABSTRACT: Paired sense and antisense (S/AS) genes located in cis represent a structural feature common to the genomes of both prokaryotes and eukaryotes, and produce partially complementary transcripts. We used published genome and transcriptome sequence data and found that over 20% of genes (645 pairs) in the budding yeast Saccharomyces cerevisiae genome are arranged in convergent pairs with overlapping 3'-UTRs. Using published microarray transcriptome data from the standard laboratory strain of S. cerevisiae, our analysis revealed that expression levels of convergent pairs are significantly negatively correlated across a broad range of environments. This implies an important role for convergent genes in the regulation of gene expression, which may compensate for the absence of RNA-dependent mechanisms such as micro RNAs in budding yeast. We selected four representative convergent gene pairs and used expression assays in wild type yeast and its genetically modified strains to explore the underlying patterns of gene expression. Results showed that convergent genes are reciprocally regulated in yeast populations and in single cells, whereby an increase in expression of one gene produces a decrease in the expression of the other, and vice-versa. Time course analysis of the cell cycle illustrated the functional significance of this relationship for the three pairs with relevant functional roles. Furthermore, a series of genetic modifications revealed that the 3'-UTR sequence plays an essential causal role in mediating transcriptional interference, which requires neither the sequence of the open reading frame nor the translation of fully functional proteins. More importantly, transcriptional interference persisted even when one of the convergent genes was expressed ectopically (in trans) and therefore does not depend on the cis arrangement of convergent genes; we conclude that the mechanism of transcriptional interference cannot be explained by the transcriptional collision model, which postulates a clash between simultaneous transcriptional processes occurring on opposite DNA strands.PLoS Genetics 01/2014; 10(1):e1004021. · 8.52 Impact Factor