NapA and NapB are the Aspergillus nidulans Nap/SET family members and NapB is a nuclear protein specifically interacting with importin alpha

14 páginas, 7 figuras, 4 figuras suplementarias, 1 tabla, 1 tabla suplementaria -- PAGS nros. 278-291In eukaryotic cells, importin α is the major carrier for transport protein cargoes into the nucleus. We characterize here kapA, the single Aspergillus nidulans gene encoding an importin α. Using an affinity approach, we identify six potential interactors of KapA50, a deleted version of KapA lacking the autoinhibitory importin-beta-binding domain. One such interactor is NapB, the A. nidulans orthologue of Saccharomyces cerevisiae Vps75p, a histone chaperone member of the Nap/SET family of proteins that additionally plays a cytosolic role in vacuolar protein sorting. NapB, but not its close relative NapA (the A. nidulans orthologue of yeast Nap1p) interacts directly with KapA50 in pull down assays, despite the fact that NapB does not contain a classical nuclear localization sequence. NapB is a nuclear protein which exits nuclei at the onset of mitosis when two simultaneous mechanisms might be acting, the partial disassembly of the nuclear pore complexes and as yet unidentified posttranslational modification of NapB. The mitotic cytosolic localization of NapB might facilitate its putative role in the sorting of protein cargoes to the vacuole. In addition, we show that NapB and the mitotic B-type cyclin NimE compete for in vitro binding to KapAWe thank Dr. Dirk Görlich for plasmid pQE80zz, Dr. Stephen Osmani for plasmid pGFP and help with confocal microscopy, J.C. Sánchez for help with the phylogenic analysis, Prof. Herbert N. Arst Jr. for critical reading of the manuscript, Leire Paz for kapG cDNA cloning and E. Reoyo for technical assistance, and the Ministerio de Ciencia y Tecnología for support through Grants BFU2006-04185 to E.A.E. and BIO2006-0556 to M.A.P. J.F.-M. and L.A.-B. held a PFPI and a FPU fellowship, respectivelyPeer reviewe

NapA and NapB are the Aspergillus nidulans Nap/SET family members and NapB is a nuclear protein specifically interacting with importin alpha

14 páginas, 7 figuras, 4 figuras suplementarias, 1 tabla, 1 tabla suplementaria -- PAGS nros. 278-291In eukaryotic cells, importin α is the major carrier for transport protein cargoes into the nucleus. We characterize here kapA, the single Aspergillus nidulans gene encoding an importin α. Using an affinity approach, we identify six potential interactors of KapA50, a deleted version of KapA lacking the autoinhibitory importin-beta-binding domain. One such interactor is NapB, the A. nidulans orthologue of Saccharomyces cerevisiae Vps75p, a histone chaperone member of the Nap/SET family of proteins that additionally plays a cytosolic role in vacuolar protein sorting. NapB, but not its close relative NapA (the A. nidulans orthologue of yeast Nap1p) interacts directly with KapA50 in pull down assays, despite the fact that NapB does not contain a classical nuclear localization sequence. NapB is a nuclear protein which exits nuclei at the onset of mitosis when two simultaneous mechanisms might be acting, the partial disassembly of the nuclear pore complexes and as yet unidentified posttranslational modification of NapB. The mitotic cytosolic localization of NapB might facilitate its putative role in the sorting of protein cargoes to the vacuole. In addition, we show that NapB and the mitotic B-type cyclin NimE compete for in vitro binding to KapAWe thank Dr. Dirk Görlich for plasmid pQE80zz, Dr. Stephen Osmani for plasmid pGFP and help with confocal microscopy, J.C. Sánchez for help with the phylogenic analysis, Prof. Herbert N. Arst Jr. for critical reading of the manuscript, Leire Paz for kapG cDNA cloning and E. Reoyo for technical assistance, and the Ministerio de Ciencia y Tecnología for support through Grants BFU2006-04185 to E.A.E. and BIO2006-0556 to M.A.P. J.F.-M. and L.A.-B. held a PFPI and a FPU fellowship, respectivelyPeer reviewe