Nuclear actin and myosin I are required for RNA polymerase I transcription.
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.
Mesh Terms:
Actins, Antibodies, Cell Line, Cell Line, Tumor, Cell Nucleus, DNA, Ribosomal, Humans, Myosin Type I, Pol1 Transcription Initiation Complex Proteins, Protein Binding, Protein Kinases, RNA Interference, RNA Polymerase I, RNA, Ribosomal, Recombinant Fusion Proteins, Ribosomal Protein S6 Kinases, Serine, Transcription Factors, Transcription, Genetic
Actins, Antibodies, Cell Line, Cell Line, Tumor, Cell Nucleus, DNA, Ribosomal, Humans, Myosin Type I, Pol1 Transcription Initiation Complex Proteins, Protein Binding, Protein Kinases, RNA Interference, RNA Polymerase I, RNA, Ribosomal, Recombinant Fusion Proteins, Ribosomal Protein S6 Kinases, Serine, Transcription Factors, Transcription, Genetic
Nat. Cell Biol.
Date: Dec. 01, 2004
PubMed ID: 15558034
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