RESUMO
Glutathione S-transferase (GST) is a dimeric detoxifying isoenzyme, involved in the deactivation of carcinogens, several tobacco-derived carcinogens, and xenobiotics. It catalyzes the reduction of glutathione to its thioester; thus, deficiency in GST activity due to homozygous deletion of the GSTT1 gene (null genotype) may play a role in the induction of lung cancer by smoking. We studied the distribution of GSTT1 gene deletion in peripheral blood DNA samples from 178 healthy controls (41 nonsmokers, 63 passive smokers and 74 smokers) and 52 lung cancer patients. Comparisons between groups showed that there was an increased lung cancer risk for individuals with the GSTT1 null genotype. Cancer patients showed significant differences when compared with controls: nonsmokers, passive smokers, and smokers. Twenty-one percent of lung cancer patients carried the deletion versus 2% among nonsmokers not exposed to passive smoking, 6% among passive smokers, and 5% among smokers. Thus, there is a significant association between this genotype and the possibility to risk of developing lung cancer.
Assuntos
Deleção de Genes , Glutationa Transferase/genética , Neoplasias Pulmonares/genética , Humanos , MéxicoRESUMO
The accumulation of the disaccharide trehalose in anhydrobiotic organisms allows them to survive severe environmental stress. A plant cDNA, SlTPS1, encoding a 109-kD protein, was isolated from the resurrection plant Selaginella lepidophylla, which accumulates high levels of trehalose. Protein-sequence comparison showed that SlTPS1 shares high similarity to trehalose-6-phosphate synthase genes from prokaryotes and eukaryotes. SlTPS1 mRNA was constitutively expressed in S. lepidophylla. DNA gel-blot analysis indicated that SlTPS1 is present as a single-copy gene. Transformation of a Saccharomyces cerevisiae tps1Delta mutant disrupted in the ScTPS1 gene with S. lepidophylla SlTPS1 restored growth on fermentable sugars and the synthesis of trehalose at high levels. Moreover, the SlTPS1 gene introduced into the tps1Delta mutant was able to complement both deficiencies: sensitivity to sublethal heat treatment at 39 degrees C and induced thermotolerance at 50 degrees C. The osmosensitive phenotype of the yeast tps1Delta mutant grown in NaCl and sorbitol was also restored by the SlTPS1 gene. Thus, SlTPS1 protein is a functional plant homolog capable of sustaining trehalose biosynthesis and could play a major role in stress tolerance in S. lepidophylla.
Assuntos
Glucosiltransferases/genética , Glucosiltransferases/metabolismo , Plantas/enzimologia , Plantas/genética , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Sequência de Aminoácidos , Sequência de Bases , Clonagem Molecular , Primers do DNA/genética , DNA Complementar/genética , DNA de Plantas/genética , Expressão Gênica , Genes Fúngicos , Genes de Plantas , Teste de Complementação Genética , Temperatura Alta , Dados de Sequência Molecular , Mutação , Saccharomyces cerevisiae/crescimento & desenvolvimento , Homologia de Sequência de Aminoácidos , Trealose/biossínteseRESUMO
We report the construction and characterization of a yeast shuttle-expression vector that can be used to express genes in yeast in a modulated form. This vector is centromeric, with a polylinker that optionally can provide an ATG start of translation. Expression features are based on the CUP1 yeast metallothionein gene promoter, which can be tightly modulated by copper.
Assuntos
Regulação Fúngica da Expressão Gênica , Vetores Genéticos , Metalotioneína/genética , Regiões Promotoras Genéticas , Saccharomyces cerevisiae/genética , Sequência de Bases , Proteínas de Transporte , Clonagem Molecular , DNA Fúngico , Dados de Sequência MolecularRESUMO
FRD, a nuclear and dominant spontaneous mutant of Saccharomyces cerevisiae capable of growing in up to 2 M NaCl, was isolated. Compared with parental cells, the mutant cells have a lower intracellular Na+/K+ ratio, shorter generation times in the presence of 1 M NaCl, and alterations in gene expression.