title: Schizosaccharomyces pombe cells lacking the Ran-binding protein Hba1 show a multidrug resistance phenotype due to constitutive nuclear accumulation of Pap1.
abstract: In Schizosaccharomyces pombe, the transcription factor Pap1, and the mitogen-activated protein kinase Sty1 are excluded from the nucleus in a Crm1-dependent manner under non-stressed conditions. Upon oxidant treatment, both Sty1 and Pap1 concentrate into the nucleus, due to an enhanced import or an impaired export. Hba1, a protein that when overexpressed confers brefeldin A resistance, contains a Ran binding domain. The purpose of this project was to understand at the molecular level the role of Hba1 in the S. pombe oxidative stress response. Fluorescent and confocal microscopy studies demonstrate that Hba1 is located at the nucleoplasm and not at the nuclear envelope. We also demonstrate that either multiple copies or deletion of the hba1 gene induces nuclear accumulation of Pap1 and Sty1. We propose that Hba1 assists Crm1 to export some nuclear export signal-containing proteins. Pap1 nuclear accumulation is sufficient for constitutive activation of its specific antioxidant response. On the contrary, constitutive nuclear localization of Sty1 in the Deltahba1 strain does not trigger the Sty1-specific, Atf1-dependent antioxidant response in the absence of stress. We conclude that the increased multidrug resistance of strains lacking or overexpressing Hba1 is due to the accumulation of Pap1 in the nucleus under non-stressed conditions.
authors.affiliation: Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, C/Dr Aiguader 80, 08003 Barcelona, Spain.
authors.forename: Esther A
authors.initials: EA
authors.lastname: Castillo
authors.forename: Ana P
authors.initials: AP
authors.lastname: Vivancos
authors.forename: Nic
authors.initials: N
authors.lastname: Jones
authors.forename: Jose
authors.initials: J
authors.lastname: Ayte
authors.forename: Elena
authors.initials: E
authors.lastname: Hidalgo
mesh_terms: D000935:Antifungal Agents / Q000494:pharmacology; D000975:Antioxidants / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors; D015153:Blotting, Western; D020126:Brefeldin A / Q000494:pharmacology; D002110:Caffeine / Q000494:pharmacology; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000096:biosynthesis*; D018432:Drug Resistance, Multiple; D005656:Fungal Proteins / Q000096:biosynthesis*; D017353:Gene Deletion; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D020928:Mitogen-Activated Protein Kinases; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000096:biosynthesis* / Q000737:chemistry; D018384:Oxidative Stress; D000073718:Pancreatitis-Associated Proteins; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012313:RNA / Q000378:metabolism; D012568:Schizosaccharomyces / Q000378:metabolism*; D029702:Schizosaccharomyces pombe Proteins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000935:Antifungal Agents; D000975:Antioxidants; D050976:Basic-Leucine Zipper Transcription Factors; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C479134:Hba1 protein, S pombe; D008164:Luminescent Proteins; D009687:Nuclear Proteins; D000073718:Pancreatitis-Associated Proteins; C105096:Pap1 protein, S pombe; C000612141:REG3A protein, human; D029702:Schizosaccharomyces pombe Proteins; D049452:Green Fluorescent Proteins; D020126:Brefeldin A; D002110:Caffeine; D012313:RNA; D017346:Protein Serine-Threonine Kinases; C499611:SRK1 protein, S pombe; D020928:Mitogen-Activated Protein Kinases