RESUMO
Damage to DNA induced by ultraviolet light can be reversed by a blue light-dependent reaction catalyzed by enzymes called DNA photolyases. Chlamydomonas has been shown to have DNA photolyase activity in both the nucleus and the chloroplast. Here we report the cloning and sequencing of a gene, PHR2, from Chlamydomonas encoding a class II DNA photolyase. The PHR2 protein, when expressed in Escherichia coli, is able to complement a DNA photolyase deficiency. The previously described Chlamydomonas mutant, phr1, which is deficient in nuclear but not chloroplast photolyase activity was shown by RFLP analysis not to be linked to the PHR2 gene. Unlike the recently reported class II DNA photolyase from Arabidopsis, the protein encoded by PHR2 is predicted to contain a chloroplast targeting sequence. This result, together with the RFLP data, suggests that PHR2 encodes the chloroplast targeted DNA photolyase.
Assuntos
Chlamydomonas/genética , Desoxirribodipirimidina Fotoliase/genética , Sequência de Aminoácidos , Animais , Southern Blotting , Chlamydomonas/enzimologia , Clonagem Molecular , DNA/química , DNA/genética , Escherichia coli/genética , Genes/genética , Teste de Complementação Genética , Isoenzimas/genética , Dados de Sequência Molecular , Mutação , Alinhamento de Sequência , Análise de Sequência de DNA , Homologia de Sequência de Aminoácidos , Transcrição GênicaRESUMO
The antizyme family consists of closely homologous proteins believed to regulate cellular polyamine pools. Antizyme1, the first described, negatively regulates ornithine decarboxylase, the initial enzyme in the biosynthetic pathway for polyamines. Antizyme1 targets ornithine decarboxylase for degradation and inhibits polyamine transport into cells, thereby diminishing polyamine pools. A polyamine-stimulated ribosomal frameshift is required for decoding antizyme1 mRNA. Recently, additional novel conserved members of the antizyme family have been described. We report here the properties of one of these, antizyme2. Antizyme2, like antizyme1, binds to ornithine decarboxylase and inhibits polyamine transport. Using a baculovirus expression system in cultured Sf21 insect cells, both antizymes were found to accelerate ornithine decarboxylase degradation. Expression of either antizyme1 or 2 in Sf21 cells also diminished their uptake of the polyamine spermidine. Both forms of antizyme can therefore function as negative regulators of polyamine production and transport. However, in contrast to antizyme1, antizyme2 has negligible ability to stimulate degradation of ornithine decarboxylase in a rabbit reticulocyte lysate.
Assuntos
Poliaminas Biogênicas/metabolismo , Ornitina Descarboxilase/metabolismo , Proteínas Ribossômicas/metabolismo , Sequência de Aminoácidos , Animais , Sequência de Bases , Transporte Biológico , Primers do DNA , Mutação da Fase de Leitura , Hidrólise , Dados de Sequência Molecular , Ligação Proteica , Coelhos , Ratos , Proteínas Ribossômicas/genética , Homologia de Sequência de Aminoácidos , SpodopteraRESUMO
Linkage disequilibrium (LD) mapping may be a powerful means for genome screening to identify susceptibility loci for common diseases. A new statistical approach for detection of LD around a disease gene is presented here. This method compares the distribution of haplotypes in affected individuals versus that expected for individuals descended from a common ancestor who carried a mutation of the disease gene. Simulations demonstrate that this method, which we term "ancestral haplotype reconstruction" (AHR), should be powerful for genome screening of phenotypes characterized by a high degree of etiologic heterogeneity, even with currently available marker maps. AHR is best suited to application in isolated populations where affected individuals are relatively recently descended (< approximately 25 generations) from a common disease mutation-bearing founder.
Assuntos
Efeito Fundador , Haplótipos , Desequilíbrio de Ligação , HumanosRESUMO
A case of a child suffering from recurrent parotitis secondary to inadvertant chewing on Stensen's duct orifice suggests that this cause may be common to other children plagued by this puzzling disorder.
Assuntos
Mucosa Bucal/lesões , Parotidite/etiologia , Bochecha/lesões , Pré-Escolar , Humanos , Masculino , Glândula Parótida/diagnóstico por imagem , Recidiva , SialografiaRESUMO
Effect of morphine sulfate on protein synthesis in rat brain was evaluated in tolerant and nontolerant rats. Male Wistar-Lewis rats were randomly distributed to control, tolerant and nontolerant groups. The rats were made tolerant by giving morphine sulfate (25 mg/kg b.i.d.) for either 42 or 84 days. An aqueous solution of 35S-methionine (0.5 muc/g b.w.t.) was administered i.v. Rats from each group were then sacrificed at 20 minutes, 1 hour and 2 hours after 35S-methionine. The 35S-activity in trichloroacetic acid-precipitated proteins and supernatant fractions from cortex, hypothalamus, putamen, corpus callosum, thalamus, cerebellum, kidney and liver was determined. In addition the amounts of label in lipid, saline-soluble and insoluble proteins of whole brain for tolerant and control rats were determined. The 35S-activity in brain proteins of non-tolerant rats did not differ from those of controls. The six brain areas in tolerant rats 1 and 2 hours after injection of 35S-methionine showed a 15 percent, then 30 percent increase in radioactivity (disintegrations per minute per milligram of protein). Proteins from putamen and corpus callosum had w/w 60 percent of the 35S-activity found in hypothalamus and cortex. There was no difference in 35S-activity in kidney and liver between control and tolerant rats. The radioactivity of the brain lipids was 2 percent of that found in proteins in both tolerant and control groups. Protein synthesis in morphine tolerant rat brain is significantly (P smaller than .01) increased as judged by incorporation of 35S-methionine.