Nuclear actin and myosin I are required for RNA polymerase I transcription

@article{Philimonenko2004NuclearAA,
  title={Nuclear actin and myosin I are required for RNA polymerase I transcription},
  author={Vlada V. Philimonenko and Jian Zhao and Sebastian Iben and Hana Dingov{\'a} and Katar{\'i}na Kysel{\'a} and Michael P. Kahle and H. Zentgraf and Wilma A. Hofmann and Primal de Lanerolle and Pavel Hoz{\'a}k and Ingrid Grummt},
  journal={Nature Cell Biology},
  year={2004},
  volume={6},
  pages={1165-1172}
}
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… 

Nuclear myosin I acts in concert with polymeric actin to drive RNA polymerase I transcription.

The results show that actin polymerization and the motor function of NM1 are required for association with the Pol I transcription machinery and transcription activation, and reveal an actomyosin-based mechanism in transcription.

Nuclear myosin I is necessary for the formation of the first phosphodiester bond during transcription initiation by RNA polymerase II

This study uses a minimal in vitro transcription system to investigate the involvement of NMI in transcription by RNA polymerase II in detail and demonstrates that NMI co‐purifies with RNA Polymerase II and that N MI is necessary for basal transcription byRNA polymerases II.

Transcription-dependent rearrangements of actin and nuclear myosin I in the nucleolus

The data support the involvement of actin and NMI in rDNA transcription and point out to other functions of these proteins in the nucleolus, such as rRNA maturation and maintenance of nucleolar architecture.

Actin and myosin in transcriptional and post-transcriptional control of gene expression

This thesis elucidates some of the molecular mechanisms through which nuclear actin controls synthesis and processing of RNA transcripts and proposes that NM1 accompanies newly assembled export-competent ribosomal subunits from nucleolus to NPC, thus modulating both their maturation and export.

Cytoskeletal protein filamin A is a nucleolar protein that suppresses ribosomal RNA gene transcription

It is shown that depletion of FLNA by siRNAs increased rRNA expression, rDNA promoter activity and cell proliferation, and these findings reveal an additional role for FLNA as a regulator of rRNA gene expression and have important implications for the understanding of the role ofFLNA in human disease.

Nuclear Myosin 1c Facilitates the Chromatin Modifications Required to Activate rRNA Gene Transcription and Cell Cycle Progression

A unique structural role for NM1 is suggested in which the interaction with SNF2h stabilizes B-WICH at the gene promoter and facilitates recruitment of the HAT PCAF, which leads to a permissive chromatin structure required for transcription activation.

Molecular functions of nuclear actin in transcription

A general model for actin in RNA polymerase II transcription is discussed whereby actin works as a conformational switch in conjunction with specific adaptors to facilitate the remodeling of large macromolecular assemblies at the promoter and along the active gene.

RNA helicase A acts as a bridging factor linking nuclear beta-actin with RNA polymerase II.

It is suggested that RHA acts as a bridging factor linking nuclear beta-actin with Pol II in PICs, and overexpression or depletion of RHA could influence the interaction of Pol II with beta- actin and beta-Actin-involved gene transcription regulation.

From transcription to transport: emerging roles for nuclear myosin I.

A recent study on intranuclear long-range chromosome movement has now demonstrated a role for NMI in the translocation of chromosome regions as well, establishing for the first time a functional role for a motor complex consisting of actin and a myosin in the nucleus.
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