title: Nuclear DNA helicase II (RNA helicase A) binds to an F-actin containing shell that surrounds the nucleolus.
abstract: Nuclear DNA helicase II (NDH II), alternatively named RNA helicase A (RHA), is an F-actin binding protein that is particularly enriched in the nucleolus of mouse cells. Here, we show that the nucleolar localization of NDH II of murine 3T3 cells depended on an ongoing rRNA synthesis. NDH II migrated out of the nucleolus after administration of 0.05 microg/ml actinomycin D, while nucleolin and the upstream binding factor (UBF) remained there. In S phase-arrested mouse cells, NDH II was frequently found at the nucleolar periphery, where it was accompanied by newly synthesized nucleolar RNA. Human NDH II was mainly distributed through the whole nucleoplasm and not enriched in the nucleoli. However, in the human breast carcinoma cell line MCF-7, NDH II was also found at the nucleolar periphery, together with the tumor suppressor protein p53. Both NDH II and p53 were apparently attached to the F-actin-based filamentous network that surrounded the nucleoli. Accordingly, this subnuclear structure was sensitive to F-actin depolymerizing agents. Depolymerization with gelsolin led to a striking accumulation of NDH II in the nucleoli of MCF-7 cells. This effect was abolished by RNase, which extensively released nucleolus-bound NDH II when added together with gelsolin. Taken together, these results support the idea that an actin-based filamentous network may anchor NDH II at the nucleolar periphery for pre-ribosomal RNA processing, ribosome assembly, and/or transport.
authors.affiliation: Department of Biochemistry, Institute of Molecular Biotechnology, Beutenbergstrasse 11, D-07708 Jena, Germany.
authors.forename: Suisheng
authors.initials: S
authors.lastname: Zhang
authors.forename: Carsten
authors.initials: C
authors.lastname: Köhler
authors.forename: Peter
authors.initials: P
authors.lastname: Hemmerich
authors.forename: Frank
authors.initials: F
authors.lastname: Grosse
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D021581:Active Transport, Cell Nucleus / Q000235:genetics; D000818:Animals; D001324:Autoantigens / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites / Q000235:genetics; D002451:Cell Compartmentation / Q000235:genetics; D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D002466:Cell Nucleolus / Q000201:enzymology* / Q000648:ultrastructure; D053487:DEAD-box RNA Helicases; D003609:Dactinomycin / Q000494:pharmacology; D018260:Gelsolin / Q000494:pharmacology; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology; D051379:Mice; D041681:NIH 3T3 Cells; D009363:Neoplasm Proteins; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D035463:Pol1 Transcription Initiation Complex Proteins / Q000235:genetics / Q000378:metabolism; D011108:Polymers / Q000378:metabolism; D011485:Protein Binding / Q000235:genetics; D020365:RNA Helicases / Q000235:genetics / Q000378:metabolism*; D012335:RNA, Ribosomal / Q000096:biosynthesis / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism; D000097796:Nucleolin
chemical_list: D000199:Actins; D001324:Autoantigens; D053487:DEAD-box RNA Helicases; D003609:Dactinomycin; D018260:Gelsolin; D006918:Hydroxyurea; D009363:Neoplasm Proteins; D010750:Phosphoproteins; D035463:Pol1 Transcription Initiation Complex Proteins; D011108:Polymers; D020365:RNA Helicases; D012335:RNA, Ribosomal; D016601:RNA-Binding Proteins; D016159:Tumor Suppressor Protein p53; D000097796:Nucleolin; C063844:transcription factor UBF; C098487:DHX9 protein, human