title: Different pathways for the nuclear import of yeast RNA polymerase II.
abstract: Recent studies suggest that RNA polymerase II (Pol II) has to be fully assembled before being imported into the nucleus, while other reports indicate a distinct mechanism to import large and small subunits. In yeast, Iwr1 binds to the holoenzyme assembled in the cytoplasm and directs its nuclear entry. However, as IWR1 is not an essential gene, Iwr1-independent pathway(s) for the nuclear import of Pol II must exist. In this paper, we investigate the transport into the nucleus of several large and small Pol II subunits in the mutants of genes involved in Pol II biogenesis. We also analyse subcellular localization in the presence of drugs that can potentially affect Pol II nuclear import. Our results show differences in the cellular distribution between large and small subunits when Pol II biogenesis was impaired. Our data suggest that, in addition to the fully assembled holoenzyme, Pol II subunits can be imported to the nucleus, either independently or as partial assemblies, through different pathways, including passive diffusion for the small subunits.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universitat de València, Burjassot 46100, Spain; E.R.I. Biotecmed, Universitat de València, Burjassot, Spain.
authors.forename: Natalia
authors.initials: N
authors.lastname: Gómez-Navarro
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Facultad de Biología, Universitat de València, Burjassot 46100, Spain; E.R.I. Biotecmed, Universitat de València, Burjassot, Spain. Electronic address: estruch@uv.es.
authors.forename: Francisco
authors.initials: F
authors.lastname: Estruch
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000502:physiology; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D012319:RNA Polymerase II / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics
chemical_list: D002352:Carrier Proteins; C544940:IWR1 protein, S cerevisiae; D012319:RNA Polymerase II
keywords: Iwr1; Nuclear import; RNA pol II biogenesis; RNA polymerase; Rtr1; Yeast