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

  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},
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.

Actin and nuclear myosin I are associated with RNAP II and function in gene transcription

Evidence is shown that both actin and NM I are associated with RNAP II in nucleus by using co-localization and co-IP assays, and they may act together on gene transcription, suggesting a direct involvement of actin-myosin complexes in regulating transcription.

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.



Actin is part of pre-initiation complexes and is necessary for transcription by RNA polymerase II

A fundamental role for actin in the initiation of transcription by RNA polymerase II is suggested after it was demonstrated that antibodies directed against β-actin, but not muscle actin, inhibited transcription in vivo and in vitro.

hRRN3 is essential in the SL1‐mediated recruitment of RNA Polymerase I to rRNA gene promoters

It is concluded that hRRN3 functions to recruit initiation‐competent Pol I to rRNA gene promoters, which suggests a mechanism for growth control of Pol I transcription.

An actin-myosin complex on actively transcribing genes.

Rrn3 Phosphorylation Is a Regulatory Checkpoint for Ribosome Biogenesis*

Results suggest that the phosphorylation state of Rrn3 regulates rDNA transcription by determining the steady-state concentration of the Rrn 3·RNA polymerase I complex within the nucleolus.

Factor C*, the specific initiation component of the mouse RNA polymerase I holoenzyme, is inactivated early in the transcription process

When elongation is halted before this critical distance, the C* remains active and on that template complex, greatly extending the kinetics of transcription and generating manyfold more transcripts than would have been synthesized if elongation had proceeded past the critical distance where C* is inactivated.

Life on a planet of its own: regulation of RNA polymerase I transcription in the nucleolus.

This review restricts the background information to the minimal level that is required for understanding initiation complex formation at the rDNA promoter before proceeding to review the regulatory pathways that adapt cellular rRNA synthesis to cell metabolism and growth.

Evidence for the Presence of Myosin I in the Nucleus*

It is proposed that the 120-kDa protein is a previously undescribed myosin I isoform that is an intranuclear actin-based molecular motor.