title: Genome-wide RNAi screen for nuclear actin reveals a network of cofilin regulators.
abstract: Nuclear actin plays an important role in many processes that regulate gene expression. Cytoplasmic actin dynamics are tightly controlled by numerous actin-binding proteins, but regulation of nuclear actin has remained unclear. Here, we performed a genome-wide RNA interference (RNAi) screen in Drosophila cells to identify proteins that influence either nuclear polymerization or import of actin. We validate 19 factors as specific hits, and show that Chinmo (known as Bach2 in mammals), SNF4Aγ (Prkag1 in mammals) and Rab18 play a role in nuclear localization of actin in both fly and mammalian cells. We identify several new regulators of cofilin activity, and characterize modulators of both cofilin kinases and phosphatase. For example, Chinmo/Bach2, which regulates nuclear actin levels also in vivo, maintains active cofilin by repressing the expression of the kinase Cdi (Tesk in mammals). Finally, we show that Nup98 and lamin are candidates for regulating nuclear actin polymerization. Our screen therefore reveals new aspects of actin regulation and links nuclear actin to many cellular processes.
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Joseph
authors.initials: J
authors.lastname: Dopie
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Eeva K
authors.initials: EK
authors.lastname: Rajakylä
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Merja S
authors.initials: MS
authors.lastname: Joensuu
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Huet
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Evelina
authors.initials: E
authors.lastname: Ferrantelli
authors.affiliation: Image and Data Analysis Core (IDAC), Harvard Medical School, Boston, MA 02115, USA.
authors.forename: Tiao
authors.initials: T
authors.lastname: Xie
authors.affiliation: Light Microscopy Unit, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland.
authors.forename: Harri
authors.initials: H
authors.lastname: Jäälinoja
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
authors.forename: Eija
authors.initials: E
authors.lastname: Jokitalo
authors.affiliation: Program in Cell and Molecular Biology, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland maria.vartiainen@helsinki.fi.
authors.forename: Maria K
authors.initials: MK
authors.lastname: Vartiainen
mesh_terms: D051339:Actin Depolymerizing Factors / Q000378:metabolism*; D000199:Actins; D000818:Animals; D002467:Cell Nucleus / Q000378:metabolism*; D017124:Conserved Sequence; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics; D019143:Evolution, Molecular; D005820:Genetic Testing; D016678:Genome; D051379:Mice; D008954:Models, Biological; D009419:Nerve Tissue Proteins / Q000378:metabolism; D010766:Phosphorylation; D058105:Polymerization; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034622:RNA Interference
chemical_list: D051339:Actin Depolymerizing Factors; D000199:Actins; C515167:Chinmo protein, Drosophila; D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; C097507:testis-specific protein kinase 1; D017346:Protein Serine-Threonine Kinases
keywords: Actin; Cofilin; Nucleus; RNA interference