Ancient animal ancestry for nuclear myosin

Hofmann, Wilma A.; Richards, Thomas A.; Lanerolle, Primal de

doi:10.1242/jcs.030205

Cited by 26 publications

(15 citation statements)

References 32 publications

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“…We next examined whether NM1 is present at the nuclear pore. The N-terminal epitope that features NM1 is rather conserved within higher vertebrates and, to a considerable extent, also in the X. laevis homologous protein (41,42). Western blot analysis on total X. laevis oocyte extracts and cultured cells confirmed the above findings and demonstrated that the anti-NM1 antibody used in this study specifically recognized the homologous X. laevis NM1 epitope (Supplemental Fig.…”

Section: A Fraction Of Nm1 Localizes At the Nuclear Pore Basket And Psupporting

confidence: 80%

Nuclear myosin 1 is in complex with mature rRNA transcripts and associates with the nuclear pore basket

et al. 2009

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In rRNA biogenesis, nuclear myosin 1 (NM1) and actin synergize to activate rRNA gene transcription. Evidence that actin is in preribosomal subunits and NM1 may control rRNA biogenesis post-transcriptionally prompted us to investigate whether NM1 associates with and accompanies rRNA to nuclear pores (NPC). Ultracentrifugation on HeLa nucleolar extracts showed RNA-dependent NM1 coelution with preribosomal subunits. In RNA immunoprecipitations (RIPs), NM1 coprecipitated with pre-rRNAs and 18S, 5.8S, and 28S rRNAs, but failed to precipitate 5S rRNA and 7SL RNA. In isolated nuclei and living HeLa cells, NM1 or actin inhibition and selective alterations in actin polymerization impaired 36S pre-rRNA processing. Immunoelectron microscopy (IEM) on sections of manually isolated Xenopus oocyte nuclei showed NM1 localization at the NPC basket. Field emission scanning IEM on isolated nuclear envelopes and intranuclear content confirmed basket localization and showed that NM1 decorates actin-rich pore-linked filaments. Finally, RIP and successive RIPs (reRIPs) on cross-linked HeLa cells demonstrated that NM1, CRM1, and Nup153 precipitate same 18S and 28S rRNAs but not 5S rRNA. We conclude that NM1 facilitates maturation and accompanies export-competent preribosomal subunits to the NPC, thus modulating export.

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Section: A Fraction Of Nm1 Localizes At the Nuclear Pore Basket And Psupporting

confidence: 80%

Nuclear myosin 1 is in complex with mature rRNA transcripts and associates with the nuclear pore basket

et al. 2009

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“…These results demonstrate that superthermal motion of chromosomal loci is not unique to E. coli. Furthermore, although myosin I has been found in the nucleus of mammalian cells (39,40), there is no evidence for nuclear localization of any myosin isoform in S. cerevisiae (41). Thus, the enhanced motion of loci in the yeast nucleus suggests that, even in eukaryotes, active fluctuations can arise from nonmyosin ATP-dependent activity.…”

Section: Resultsmentioning

confidence: 99%

Nonthermal ATP-dependent fluctuations contribute to the in vivo motion of chromosomal loci

Weber

Spakowitz

Theriot

2012

Proc. Natl. Acad. Sci. U.S.A.

328

313

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Chromosomal loci jiggle in place between segregation events in prokaryotic cells and during interphase in eukaryotic nuclei. This motion seems random and is often attributed to Brownian motion. However, we show here that locus dynamics in live bacteria and yeast are sensitive to metabolic activity. When ATP synthesis is inhibited, the apparent diffusion coefficient decreases, whereas the subdiffusive scaling exponent remains constant. Furthermore, the magnitude of locus motion increases more steeply with temperature in untreated cells than in ATP-depleted cells. This "superthermal" response suggests that untreated cells have an additional source of molecular agitation, beyond thermal motion, that increases sharply with temperature. Such ATP-dependent fluctuations are likely mechanical, because the heat dissipated from metabolic processes is insufficient to account for the difference in locus motion between untreated and ATP-depleted cells. Our data indicate that ATP-dependent enzymatic activity, in addition to thermal fluctuations, contributes to the molecular agitation driving random (sub)diffusive motion in the living cell.T he cytoplasm is a crowded and dynamic medium, with molecules constantly jostling around and colliding with each other. This molecular motion is often attributed to Brownian motion, the random movement of suspended particles driven by thermal fluctuations of the solvent (1, 2). Classic Brownian motion theory assumes a system at thermal equilibrium. However, cells are far from equilibrium. They use the chemical energy of ATP (and GTP) to drive active biological processes, such as transport and metabolism.Recent work in eukaryotic cells demonstrates that biological activity generates nonthermal fluctuations of greater magnitude than thermal fluctuations (3-8). These active fluctuations can drive diffusive-like motion of molecules inside the cell, a phenomenon known as "active" diffusion (9, 10). In vitro experiments and analytical theory suggest that these active fluctuations are generated by the cytoskeletal molecular motor myosin (11-13). Thus, random molecular motion in vivo, at least in eukaryotic cytoplasm, may be due to active motor-driven forces in addition to passive thermal forces.Here we present evidence suggesting that ATP-dependent fluctuations contribute to the motion of chromosomal loci in bacterial and yeast cells. By modulating the temperature at which cells are observed, we were able to identify nonthermal forces that contribute to intracellular motion. Unlike active microrheology (7,8,11), temperature modulation presents a simple perturbation that can be applied to any experimental system to explore the physical processes underlying molecular motion in vivo. Our results suggest that "active" diffusion is not unique to systems containing eukaryotic cytoskeletal motors. This phenomenon may in fact be a general property of macromolecular motion in all living cells. Resultsis calculated to determine the subdiffusive scaling exponent α and the apparent diffusion coefficient D ap...

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“…However, actin evolved long before the first myosin (Goodson and Hawse, 2002;Hofmann et al, 2009;Pollard and Cooper, 2009) and actin must have had essential, conserved functions that predated myosin-mediated force production. Importantly, our data suggest roles for nuclear actin that are independent of its ability to form canonical filaments.…”

Section: Discussionmentioning

confidence: 99%

Persistent nuclear actin filaments inhibit transcription by RNA polymerase II

Serebryannyy

Parilla

Annibale

et al. 2016

Journal of Cell Science

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Actin is abundant in the nucleus and it is clear that nuclear actin has important functions. However, mystery surrounds the absence of classical actin filaments in the nucleus. To address this question, we investigated how polymerizing nuclear actin into persistent nuclear actin filaments affected transcription by RNA polymerase II. Nuclear filaments impaired nuclear actin dynamics by polymerizing and sequestering nuclear actin. Polymerizing actin into stable nuclear filaments disrupted the interaction of actin with RNA polymerase II and correlated with impaired RNA polymerase II localization, dynamics, gene recruitment, and reduced global transcription and cell proliferation. Polymerizing and crosslinking nuclear actin in vitro similarly disrupted the actin-RNA-polymerase-II interaction and inhibited transcription. These data rationalize the general absence of stable actin filaments in mammalian somatic nuclei. They also suggest a dynamic pool of nuclear actin is required for the proper localization and activity of RNA polymerase II.

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Ancient animal ancestry for nuclear myosin

Cited by 26 publications

References 32 publications

Nuclear myosin 1 is in complex with mature rRNA transcripts and associates with the nuclear pore basket

Nuclear myosin 1 is in complex with mature rRNA transcripts and associates with the nuclear pore basket

Nonthermal ATP-dependent fluctuations contribute to the in vivo motion of chromosomal loci

Persistent nuclear actin filaments inhibit transcription by RNA polymerase II

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