Article abstract
Nature Cell Biology 6, 1165 - 1172 (2004)
Published online: 21 November 2004 | doi:10.1038/ncb1190
Nuclear actin and myosin I are required for RNA polymerase I transcription
Vlada V. Philimonenko1,5, Jian Zhao2,5, Sebastian Iben2, Hana Dingová1, Katarína Kyselá1, Michal Kahle1, Hanswalter Zentgraf3, Wilma A. Hofmann4, Primal de Lanerolle4, Pavel Hozák1 & Ingrid Grummt2
Abstract
The presence of actin and nuclear myosin I (NMI) in the nucleus suggests a role for these motor proteins in nuclear functions. We have investigated the role of actin and nuclear myosin I (NMI) in the transcription of ribosomal RNA genes (rDNA). Both proteins are associated with rDNA and are required for RNA polymerase I (Pol I) transcription. Microinjection of antibodies against actin or NMI, as well as short interfering RNA-mediated depletion of NMI, decreased Pol I transcription in vivo, whereas overexpression of NMI augmented pre-rRNA synthesis. In vitro, recombinant NMI activated Pol I transcription, and antibodies to NMI or actin inhibited Pol I transcription both on naked DNA and pre-assembled chromatin templates. Whereas actin associated with Pol I, NMI bound to Pol I through the transcription-initiation factor TIF-IA. The association with Pol I requires phosphorylation of TIF-IA at Ser 649 by RSK kinase, indicating a role for NMI in the growth-dependent regulation of rRNA synthesis.
- Department of Cell Ultrastructure and Molecular Biology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague 14220, Czech Republic.
- Division of Molecular Biology of the Cell II, German Cancer Research Center, D-69118 Heidelberg, Germany.
- Applied Tumorvirology, German Cancer Research Center, D-69118 Heidelberg, Germany.
- Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago IL 60612, USA.
- These authors contributed equally to this work.
Correspondence to: Ingrid Grummt2 e-mail: i.grummt@dkfz.de
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