Nuclear actin filaments recruit cofilin and actin-related protein 3, and their formation is connected with a mitotic blockReport as inadecuate

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Histochemistry and Cell Biology

, Volume 142, Issue 2, pp 139–152

First Online: 08 July 2014Accepted: 25 June 2014DOI: 10.1007-s00418-014-1243-9

Cite this article as: Kalendová, A., Kalasová, I., Yamazaki, S. et al. Histochem Cell Biol 2014 142: 139. doi:10.1007-s00418-014-1243-9


Although actin monomers polymerize into filaments in the cytoplasm, the form of actin in the nucleus remains elusive. We searched for the form and function of β-actin fused to nuclear localization signal and to enhanced yellow fluorescent protein EN-actin. Our results reveal that EN-actin is either dispersed in the nucleoplasm homogenous EN-actin or forms bundled filaments in the nucleus EN-actin filaments. Formation of such filaments was not connected with increased EN-actin levels. Among numerous actin-binding proteins tested, only cofilin is recruited to the EN-actin filaments. Overexpression of EN-actin causes increase in the nuclear levels of actin-related protein 3 Arp3. Although Arp3, a member of actin nucleation complex Arp2-3, is responsible for EN-actin filament nucleation and bundling, the way cofilin affects nuclear EN-actin filaments dynamics is not clear. While cells with homogenous EN-actin maintained unaffected mitosis during which EN-actin re-localizes to the plasma membrane, generation of nuclear EN-actin filaments severely decreases cell proliferation and interferes with mitotic progress. The introduction of EN-actin manifests in two mitotic-inborn defects—formation of binucleic cells and generation of micronuclei—suggesting that cells suffer aberrant cytokinesis and-or impaired chromosomal segregation. In interphase, nuclear EN-actin filaments passed through chromatin region, but do not co-localize with either chromatin remodeling complexes or RNA polymerases I and II. Surprisingly presence of EN-actin filaments was connected with increase in the overall transcription levels in the S-phase by yet unknown mechanism. Taken together, EN-actin can form filaments in the nucleus which affect important cellular processes such as transcription and mitosis.

KeywordsNuclear actin Transcription Mitosis Actin-related protein 3 Cofilin  Download fulltext PDF

Author: Alžběta Kalendová - Ilona Kalasová - Shota Yamazaki - Lívia Uličná - Masahiko Harata - Pavel Hozák



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