RESUMEN
The molecular mechanism underlying the retention of intron-containing mRNAs in the nucleus is not understood. Here, we show that retention of intron-containing mRNAs in yeast is mediated by perinuclearly located Mlp1. Deletion of MLP1 impairs retention while having no effect on mRNA splicing. The Mlp1-dependent leakage of intron-containing RNAs is increased in presence of ts-prp18 delta, a splicing mutant. When overall pre-mRNA levels are increased by deletion of RRP6, a nuclear exosome component, MLP1 deletion augments leakage of only the intron-containing portion of mRNAs. Our data suggest, moreover, that Mlp1-dependent retention is mediated via the 5' splice site. Intriguingly, we found Mlp-proteins to be present only on sections of the NE adjacent to chromatin. We propose that at this confined site the perinuclear Mlp1 implements a quality control step prior to export, physically retaining faulty pre-mRNAs.
Asunto(s)
Núcleo Celular/genética , Proteínas Nucleares/genética , Empalme del ARN/genética , ARN Mensajero/genética , Proteínas de Saccharomyces cerevisiae/genética , Levaduras/genética , Transporte Activo de Núcleo Celular/genética , Núcleo Celular/metabolismo , Exorribonucleasas/deficiencia , Exorribonucleasas/genética , Complejo Multienzimático de Ribonucleasas del Exosoma , Intrones/genética , Mutación/genética , Membrana Nuclear/genética , Membrana Nuclear/metabolismo , Proteínas de Complejo Poro Nuclear/genética , Proteínas de Complejo Poro Nuclear/metabolismo , Proteínas Nucleares/deficiencia , Proteínas Nucleares/metabolismo , Transporte de Proteínas/genética , Sitios de Empalme de ARN/genética , ARN Mensajero/metabolismo , Proteínas de Unión al ARN , Ribonucleoproteína Nuclear Pequeña U5 , Proteínas de Saccharomyces cerevisiae/metabolismo , Levaduras/metabolismoRESUMEN
The Aurora B kinase complex is a critical regulator of chromosome segregation and cytokinesis. In Caenorhabditis elegans, AIR-2 (Aurora B) function requires ICP-1 (Incenp) and BIR-1 (Survivin). In various systems, Aurora B binds to orthologues of these proteins. Through genetic analysis, we have identified a new subunit of the Aurora B kinase complex, CSC-1. C. elegans embryos depleted of CSC-1, AIR-2, ICP-1, or BIR-1 have identical phenotypes. CSC-1, BIR-1, and ICP-1 are interdependent for their localization, and all are required for AIR-2 localization. In vitro, CSC-1 binds directly to BIR-1. The CSC-1/BIR-1 complex, but not the individual subunits, associates with ICP-1. CSC-1 associates with ICP-1, BIR-1, and AIR-2 in vivo. ICP-1 dramatically stimulates AIR-2 kinase activity. This activity is not stimulated by CSC-1/BIR-1, suggesting that these two subunits function as targeting subunits for AIR-2 kinase.