RESUMEN
Nocturnin (NOCT) is a eukaryotic enzyme that belongs to a superfamily of exoribonucleases, endonucleases, and phosphatases. In this study, we analyze the expression, processing, localization, and cellular functions of human NOCT. We find that NOCT protein is differentially expressed and processed in a cell and tissue type-specific manner to control its localization to the cytoplasm or mitochondrial exterior or interior. The N terminus of NOCT is necessary and sufficient to confer import and processing in the mitochondria. We measured the impact of cytoplasmic NOCT on the transcriptome and observed that it affects mRNA levels of hundreds of genes that are significantly enriched in osteoblast, neuronal, and mitochondrial functions. Recent biochemical data indicate that NOCT dephosphorylates NADP(H) metabolites, and thus we measured the effect of NOCT on these cofactors in cells. We find that NOCT increases NAD(H) and decreases NADP(H) levels in a manner dependent on its intracellular localization. Collectively, our data indicate that NOCT can regulate levels of both mRNAs and NADP(H) cofactors in a manner specified by its location in cells.
Asunto(s)
NAD/metabolismo , Proteínas Nucleares/metabolismo , ARN Mensajero/metabolismo , Factores de Transcripción/metabolismo , Adenosina Trifosfato/metabolismo , Animales , Citoplasma/metabolismo , Células HEK293 , Células Hep G2 , Humanos , Ratones , Mitocondrias/metabolismo , Proteínas Nucleares/genética , Procesamiento Proteico-Postraduccional , Factores de Transcripción/genética , TranscriptomaRESUMEN
Post-transcriptional control of messenger RNA (mRNA) is an important layer of gene regulation that modulates mRNA decay, translation, and localization. Eukaryotic mRNA decay begins with the catalytic removal of the 3' poly-adenosine tail by deadenylase enzymes. Multiple deadenylases have been identified in vertebrates and are known to have distinct biological roles; among these proteins is Nocturnin, which has been linked to circadian biology, adipogenesis, osteogenesis, and obesity. Multiple studies have investigated Nocturnin's involvement in these processes; however, a full understanding of its molecular function remains elusive. Recent studies have provided new insights by identifying putative Nocturnin-regulated mRNAs in mice and by determining the structure and regulatory activities of human Nocturnin. This review seeks to integrate these new discoveries into our understanding of Nocturnin's regulatory functions and highlight the important remaining unanswered questions surrounding its regulation, biochemical activities, protein partners, and target mRNAs.
Asunto(s)
Ritmo Circadiano/genética , Proteínas Nucleares/genética , Procesamiento Postranscripcional del ARN/genética , ARN Mensajero/genética , Factores de Transcripción/genética , Animales , Exorribonucleasas/genética , Regulación de la Expresión Génica/genética , Humanos , Ratones , Estabilidad del ARN/genética , Vertebrados/genéticaRESUMEN
Sequencing of the Mycobacterium tuberculosis pncA gene allows for pyrazinamide susceptibility testing. We summarize data on pncA polymorphisms that do not confer resistance at a susceptibility breakpoint of 100 µg/ml pyrazinamide in MGIT within a cohort of isolates from South Africa and the U.S. Centers for Disease Control and Prevention.