title: HelF, a putative RNA helicase acts as a nuclear suppressor of RNAi but not antisense mediated gene silencing.
abstract: We have identified a putative RNA helicase from Dictyostelium that is closely related to drh-1, the 'dicer-related-helicase' from Caenorhabditis elegans and that also has significant similarity to proteins from vertebrates and plants. Green fluorescent protein (GFP)-tagged HelF protein was localized in speckles in the nucleus. Disruption of the helF gene resulted in a mutant morphology in late development. When transformed with RNAi constructs, HelF- cells displayed enhanced RNA interference on four tested genes. One gene that could not be knocked-down in the wild-type background was efficiently silenced in the mutant. Furthermore, the efficiency of silencing in the wild-type was dramatically improved when helF was disrupted in a secondary transformation. Silencing efficiency depended on transcription levels of hairpin RNA and the threshold was dramatically reduced in HelF- cells. However, the amount of siRNA did not depend on hairpin transcription. HelF is thus a natural nuclear suppressor of RNA interference. In contrast, no improvement of gene silencing was observed when mutant cells were challenged with corresponding antisense constructs. This indicates that RNAi and antisense have distinct requirements even though they may share parts of their pathways.
authors.affiliation: Abt. Genetik, Universität Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, Germany.
authors.forename: Blagovesta
authors.initials: B
authors.lastname: Popova
authors.forename: Markus
authors.initials: M
authors.lastname: Kuhlmann
authors.forename: Andrea
authors.initials: A
authors.lastname: Hinas
authors.forename: Fredrik
authors.initials: F
authors.lastname: Söderbom
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Nellen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry; D002460:Cell Line; D002467:Cell Nucleus / Q000201:enzymology; D053487:DEAD-box RNA Helicases; D004023:Dictyostelium / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D017353:Gene Deletion; D020868:Gene Silencing; D008124:Locomotion; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D020365:RNA Helicases / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D034622:RNA Interference; D016372:RNA, Antisense / Q000235:genetics; D012330:RNA, Double-Stranded / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
chemical_list: D029742:Caenorhabditis elegans Proteins; D009687:Nuclear Proteins; D016372:RNA, Antisense; D012330:RNA, Double-Stranded; C461646:DRH-1 protein, C elegans; D053487:DEAD-box RNA Helicases; D020365:RNA Helicases