RESUMO
The yeast Saccharomyces cerevisiae has a finite life span that is measured by the number of times the individual cell divides. The gene coding for one of several transcripts that are differentially expressed during the replicative life span has been cloned. The nucleotide sequence revealed an open reading frame capable of encoding a transmembrane protein of 411 amino acids that displays no significant similarities to any known proteins. Nevertheless, sequences similar to this gene were found in several mammals, including humans. The transcript levels decreased with replicative age of yeast cells. A gene deletion in haploid cells resulted in a pronounced increase (approximately 50%) in mean and in maximum life span. These results indicate that this gene, which we call LAG1, plays a role in determining yeast longevity.
Assuntos
Proteínas Fúngicas/genética , Genes Fúngicos , Proteínas de Membrana/genética , Proteínas de Saccharomyces cerevisiae , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/fisiologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Northern Blotting , Southern Blotting , Mapeamento Cromossômico , Clonagem Molecular , DNA Fúngico/química , DNA Fúngico/genética , Proteínas Fúngicas/química , Deleção de Genes , Expressão Gênica , Humanos , Mamíferos , Proteínas de Membrana/química , Dados de Sequência Molecular , Fases de Leitura Aberta , Estrutura Secundária de Proteína , RNA Fúngico/análise , RNA Fúngico/biossíntese , Mapeamento por Restrição , Saccharomyces cerevisiae/crescimento & desenvolvimento , Fatores de Tempo , Transcrição GênicaRESUMO
It has been proposed that a decrease in the length of telomeres with the successive rounds of DNA replication that accompany mitotic division could play a causal role in the aging process. To investigate this possibility, telomeres from cells of the budding yeast Saccharomyces cerevisiae that varied in replicative age were examined. No change in the lengths of the telomeres was observed in cells that had completed up to 83% of the mean life span. We conclude that the length of the telomeres is not a contributing factor in the natural aging process in individual yeast cells.
