Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.7.6 (RNA polymerase)
 34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nuclear DNA helicase II (NDH II) is a highly conserved member of the DEXH superfamily of eukaryotic helicases, whose physiological role is still unclear. To explore the function of NDH II, we studied the intracellular distribution of NDH II of different mammalian species by immunofluorescence and compared these findings with the known role of the Drosophila homologue MLE that is involved in sex-specific gene dosage compensation. NDH II displayed an apparent nucleolar localization in murine cells, whereas in cells from all other mammalian species examined so far the protein was confined to the nucleoplasm and apparently excluded from the nucleoli. The nucleolar localization of mouse NDH II strongly suggests a role in ribosomal RNA biosynthesis. Immunoelectron microscopic studies revealed that the mouse NDH II was found at the dense fibrillar components of the nucleoli, and a significant percentage of NDH II molecules colocalized with the RNA polymerase I (Pol I) transcription factor UBF (upstream binding factor). Additionally, the nucleolar localization of NDH II coincided with a preferential immunolabeling pattern of nascent transcripts with bromouridine (BrUMP). Furthermore, mouse NDH II redistributed in mitosis in a manner highly correlated with Pol I activity. Conditions leading to the inhibition of Pol I activity in the interphase decreased the amount of NDH II in the nucleoli that diffused into the nucleoplasm and the cytosol. Contrary to the effect of inhibiting rRNA synthesis, treatment of mouse cells with the translation inhibitor cycloheximide did not compromise the nucleolar localization of murine NDH II.
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PMID:Nucleolar localization of murine nuclear DNA helicase II (RNA helicase A). 1041 77

Nuclear DNA helicase II (NDH II), also designated RNA helicase A, is a multifunctional protein involved in transcription, RNA processing, and transport. Here we report that NDH II binds to F-actin. NDH II was partially purified from HeLa nuclear extracts by ion-exchange chromatography on Bio-Rex 70 and DEAE-Sepharose. Upon gel-filtration chromatography on Sepharose 4B, partially purified NDH II resolved into two distinct peaks. The first NDH II peak, corresponding to the void volume of Sepharose 4B, displayed coelution with an abundant 42-kDa protein that was subsequently identified as actin. Several nuclear proteins such as RNA polymerase II, the U5 small nuclear ribonucleoprotein (RNP)-associated WD40 protein, and heterogeneous nuclear RNPs (hnRNPs) copurified with NDH II. However, only hnRNPs A1 and C were found together with NDH II and actin polymers during gel filtration. NDH II and hnRNP C from the HeLa nuclear extract coeluted with F-actin on Sepharose 4B in an RNase-resistant manner, whereas hnRNP A1 was nearly completely removed from F-actin-associated hnRNP complexes following RNA digestion. The association of NDH II and hnRNP C with F-actin was abolished by gelsolin, an F-actin-depolymerizing protein that fragments actin polymers into oligomers or monomers. Furthermore, NDH II co-immunoprecipitated with F-actin and hnRNP C, respectively. In vitro translated NDH II coeluted with F-actin on Sepharose 4B, whereas no coelution with F-actin was observed for in vitro translated hnRNP A1 or C1. Binding to F-actin requires an intact C terminus of NDH II and most likely a native protein conformation. Electron microscopy indicated a close spatial proximity among NDH II, hnRNP C, and F-actin within the HeLa nucleus. These results suggest an important function of NDH II in mediating the attachment of hnRNP-mRPP RNP complexes to the actin nucleoskeleton for RNA processing, transport, or other actin-related processes.
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PMID:Nuclear DNA helicase II/RNA helicase A binds to filamentous actin. 1168 88

It is known that nuclear DNA helicase II (NDH II) links CREB-binding protein directly to RNA polymerase II holoenzyme, and that this interaction is essential for gene activation by CREB. Here, we report for the first time that some NDH II/RNA helicase A is a component of promyelocytic leukemia nuclear bodies (PML NBs). An autoimmune serum specific for PML NBs was identified and used in immunoprecipitation experiments. NDH II was present in the immunoprecipitates as shown by mass spectrometry and by immunoblotting. Immunofluorescence and ultrastructural studies showed that NDH II colocalizes with a small subset of PML NBs in control cells, however, colocalizes with practically all bodies in interferon-alpha-stimulated cells. After interferon stimulation, more PML NBs were found to contain newly synthesized RNA, as indicated by bromouridine incorporation. PML NBs also contain RNA polymerase II. The association of NDH II with PML NBs was transcriptionally dependent, and NDH II was present in all bodies with nascent RNA. Blocking of mRNA synthesis caused NDH II relocalization from nucleoplasm to nucleoli. Based on the data, we suggest that NDH II recruitment to PML NBs is connected with transcriptional regulation of interferon-alpha-inducible genes attached to PML NBs.
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PMID:Nuclear DNA helicase II is recruited to IFN-alpha-activated transcription sites at PML nuclear bodies. 1216 69

Nuclear DNA helicase II (NDH II) is a member of the DEAH superfamily of helicases and functions as a pre-mRNA- and mRNA-binding protein in human cells. Here we report for the first time that human NDH II is associated with the nucleolus of transformed and nontransformed cells as shown by immunofluorescence and by ultrastructural studies. When RNA polymerase II (POL II) transcription is inhibited, NDH II highly accumulates in the nucleolus and shows predominant association with subdomains in DFC and in a portion of GC attached to DFC. Furthermore, these subdomains completely co-localize with mRNA-binding protein TLS. In addition, we show that nucleolar accumulation of NDH II is closely related to G(0)-phase growth arrest in human fibroblasts. Thus, the nucleolar localization of NDH II depends upon the metabolic state of the cell. Based on the data we propose that NDH II operates in both nucleoplasmic and nucleolar mode, and that its redistribution reflects accumulations indicating a possible cycling of NDH II between nucleoplasm and the nucleolus. The nucleolus can serve as a temporary storage or recycling center for NDH II. Possible functions of NDH II in pre-rRNA biogenesis, or in nucleolar mRNA metabolism, are also discussed.
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PMID:The localization of nuclear DNA helicase II in different nuclear compartments is linked to transcription. 1224 51