RESUMO
In yeast the UPF1, UPF2 and UPF3 genes encode three interacting factors involved in translation termination and nonsense-mediated mRNA decay (NMD). UPF1 plays a central role in both processes. In addition, UPF1 was originally isolated as a multicopy suppressor of mitochondrial splicing deficiency, and its deletion leads to an impairment in respiratory growth. Here, we provide evidence that inactivation of UPF2 or UPF3, like that of UPF1, leads to an impairment in respiratory competence, suggesting that their products, Upf1p, Upf2p and Upf3p, are equivalently involved in mitochondrial biogenesis. In addition, however, we show that only Upf1p acts as a multicopy suppressor of mitochondrial splicing deficiency, and its activity does not require either Upf2p or Upf3p. Mutations in the conserved cysteine- and histidine-rich regions and ATPase and helicase motifs of Upf1p separate the ability of Upf1p to complement the respiratory impairment of a Deltaupf1 strain from its ability to act as a multicopy suppressor of mitochondrial splicing deficiency, indicating that distinct pathways express these phenotypes. In addition, we show that, when overexpressed, Upf1p is not detected within mitochondria, suggesting that its role as multicopy suppressor of mitochondrial splicing deficiency is indirect. Furthermore, we provide evidence that cells overexpressing certain upf1 alleles accumulate a phosphorylated isoform of Upf1p. Altogether, these results indicate that overexpression of Upf1p compensates for mitochondrial splicing deficiency independently of its role in mRNA surveillance, which relies on Upf1p-Upf2p-Upf3p functional interplay.
Assuntos
Mitocôndrias/metabolismo , RNA Helicases/genética , RNA Helicases/fisiologia , Splicing de RNA , RNA Mensageiro/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Motivos de Aminoácidos , Análise Mutacional de DNA , Inativação Gênica , Genes Fúngicos , Teste de Complementação Genética , Mutação , Consumo de Oxigênio , Terminação Traducional da Cadeia Peptídica , Fosforilação , Biossíntese de Proteínas , RNA Helicases/metabolismo , Processamento Pós-Transcricional do RNA , RNA Fúngico/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/fisiologia , Saccharomyces cerevisiae/crescimento & desenvolvimento , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/fisiologia , Supressão Genética , Transativadores/genética , Transativadores/fisiologiaRESUMO
MitBASE is an integrated and comprehensive database of mitochondrial DNA data which collects all available information from different organisms and from intraspecie variants and mutants. Research institutions from different countries are involved, each in charge of developing, collecting and annotating data for the organisms they are specialised in. The design of the actual structure of the database and its implementation in a user-friendly format are the care of the European Bioinformatics Institute. The database can be accessed on the Web at the following address: http://www.ebi.ac. uk/htbin/Mitbase/mitbase.pl. The impact of this project is intended for both basic and applied research. The study of mitochondrial genetic diseases and mitochondrial DNA intraspecie diversity are key topics in several biotechnological fields. The database has been funded within the EU Biotechnology programme.
Assuntos
DNA Mitocondrial/genética , Bases de Dados Factuais , Animais , Núcleo Celular/genética , Classificação , DNA Mitocondrial/classificação , Eucariotos/genética , Europa (Continente) , Fungos/genética , Código Genético , Doenças Genéticas Inatas/genética , Variação Genética , Humanos , Armazenamento e Recuperação da Informação , Internet , Invertebrados/genética , Mutação , Plantas/genética , Interface Usuário-Computador , Vertebrados/genéticaRESUMO
In the framework of the EU BIOTECH PROGRAM and within the 'MITBASE: a comprehensive and integrated database on mtDNA' project, we have prepared a pilot database (MitBASE Pilot) on nuclear genes involved in mitochondrial biogenesis and its regulation in Saccharomyces cerevisiae. MitBASE Pilot includes nuclear genes encoding mitochondrial proteins as well as nuclear genes encoding products which are localised in other sub-cellular compartments but nevertheless interact with mitochondrial functions. Genes have been classified on the basis of the mitochondrial process in which they participate and the mitochondrial phenotype of the gene knockout. The structure of the MitBASE Pilot database has been conceived for a flexible organisation of the information. An intuitive visual query system has been developed which allows users to select information in different combinations, both in the query and the output format, according to their needs. MitBASE Pilot is a relational database, is maintained at the EMBL-European Bioinformatics Institute (EBI) and is available at the World Wide Web site http://www3.ebi.ac. uk/Research/Mitbase/mitbiog.pl
Assuntos
Bases de Dados Factuais , Genes Fúngicos/genética , Mitocôndrias/fisiologia , Saccharomyces cerevisiae/genética , Núcleo Celular/genética , Proteínas Fúngicas/química , Proteínas Fúngicas/genética , Proteínas Fúngicas/metabolismo , Regulação Fúngica da Expressão Gênica , Armazenamento e Recuperação da Informação , Internet , Mitocôndrias/genética , Saccharomyces cerevisiae/crescimento & desenvolvimentoRESUMO
The two adjacent nuclear genes ISF1 and NAM7 cooperatively participate in mitochondrial functions. It is well known that Cyp1p(Hap1p) activates a number of genes involved in these same functions. We show in this paper that Cyp1p influences the transcriptional regulation of NAM7. In addition, a significant amount of ISF1-NAM7 cotranscript is observed in a cyp1 mutant context. An extensive analysis of the intergenic region which separates the two genes revealed 5' starts of the NAM7 transcripts, additional to those previously mapped. These new 5' starts overlap the 3' ends of ISF1. We propose that NAM7 is under the control of a negative Cyp1p-dependent regulator and that its absence favours a transcriptional read-through which results in the ISF1-NAM7 cotranscript we have identified.
