RESUMO
Replication-associated histone genes encode the only metazoan mRNAs that lack polyA tails, ending instead in a conserved 26-nt sequence that forms a stem-loop. Most of the regulation of mammalian histone mRNA is posttranscriptional and mediated by this unique 3' end. Stem-loop-binding protein (SLBP) binds to the histone mRNA 3' end and is thought to participate in all aspects of histone mRNA metabolism, including cell cycle regulation. To examine SLBP function genetically, we have cloned the gene encoding Drosophila SLBP (dSLBP) by a yeast three-hybrid method and have isolated mutations in dSLBP. dSLBP function is required both zygotically and maternally. Strong dSLBP alleles cause zygotic lethality late in development and result in production of stable histone mRNA that accumulates in nonreplicating cells. These histone mRNAs are cytoplasmic and have polyadenylated 3' ends like other polymerase II transcripts. Hypomorphic dSLBP alleles support zygotic development but cause female sterility. Eggs from these females contain dramatically reduced levels of histone mRNA, and mutant embryos are not able to complete the syncytial embryonic cycles. This is in part because of a failure of chromosome condensation at mitosis that blocks normal anaphase. These data demonstrate that dSLBP is required in vivo for 3' end processing of histone pre-mRNA, and that this is an essential function for development. Moreover, dSLBP-dependent processing plays an important role in coupling histone mRNA production with the cell cycle.
Assuntos
Proteínas de Drosophila , Drosophila/genética , Drosophila/metabolismo , Histonas/metabolismo , Proteínas de Insetos/genética , Proteínas de Insetos/metabolismo , Proteínas Nucleares , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas de Xenopus , Fatores de Poliadenilação e Clivagem de mRNA , Sequência de Aminoácidos , Animais , Sequência de Bases , Ciclo Celular , Clonagem Molecular , DNA Complementar/genética , DNA Complementar/isolamento & purificação , Drosophila/citologia , Drosophila/embriologia , Feminino , Genes de Insetos , Dados de Sequência Molecular , Mutação , Oócitos/metabolismo , Processamento Pós-Transcricional do RNA , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , XenopusRESUMO
This study investigates the effect of ethanol ingestion on antioxidant enzymes (AOE) and lipid peroxidation (malondialdehyde, (MDA) in different brain regions of the rat after acute exercise. Acute exercise (100% VO2max) significantly increased glutathione peroxidase (GSH-Px) activity and decreased glutathione reductase (GR) activity in the cerebral cortex. Acute exercise significantly increased MDA level in the corpus striatum. Ethanol (20%) (1.6 g/kg, PO) significantly increased MDA level in the cerebral cortex. Ethanol also significantly increased superoxide dismutase (SOD) activity in the cortex and catalase (CAT), GSH-Px, and GR activities in the corpus striatum. Ethanol significantly augmented CAT activity in the medulla and GSH-Px activity in the hypothalamus. However, CAT activity significantly decreased in the hypothalamus after ethanol ingestion. The combination significantly increased GSH-Px activity in the hypothalamus, SOD activity in the cortex, GR activity in the striatum, and MDA level in the medulla. In conclusion, the cerebral cortex, striatum medulla, and hypothalamus reacted differentially in response to ethanol as well as to acute exercise-induced oxidative stress whereas the combination moderated the changes in AOE activity in specific brain regions.