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. 2021 Jun 23;10(7):1582. doi: 10.3390/cells10071582

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© 2021 by the authors.

Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).

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The speckles acting as radial spring pumps anchored between the nucleolar and perinuclear flexibly rigid heterochromatin shells and equipped by elastic actomyosin elements integrate the radial-concentric nuclear order for transcription pulsing. (a,b) EM thin sections of rat ascitic Zajdela hepatoma cells: (a) The links of the speckle (ICG) to the perinucleolar and perinuclear heterochromatin (arrows), Nl—nucleolus; (b) the view of the radial-concentric speckle substructure as revealed on shortly cold-PF-prefixed cells after short DNAse I treatment with 4.5 mM MgCl₂ in phosphate buffer/sucrose before dehydration and epoxy-embedment (conventional contrasting). ICG—speckle, HR—heterochromatin, Nl—nucleolus. Republished from [53]. (c) The representative image of the circular-radial self-organization of F-actin filaments (stained by phalloidin) of human foreskin fibroblasts, structured soon after seeding on isotropic substrate; from [108]. (d) Schematic of the functional transcriptional relay in its relationship with speckles and the concentric rings of the nucleolar and perinuclear heterochromatin shells, deduced from experiments with suppression of RNA synthesis and the literature on the participation of the nuclear cytoskeleton in it. Modified from [107].

The speckles acting as radial spring pumps anchored between the nucleolar and perinuclear flexibly rigid heterochromatin shells and equipped by elastic actomyosin elements integrate the radial-concentric nuclear order for transcription pulsing. (a,b) EM thin sections of rat ascitic Zajdela hepatoma cells: (a) The links of the speckle (ICG) to the perinucleolar and perinuclear heterochromatin (arrows), Nl—nucleolus; (b) the view of the radial-concentric speckle substructure as revealed on shortly cold-PF-prefixed cells after short DNAse I treatment with 4.5 mM MgCl₂ in phosphate buffer/sucrose before dehydration and epoxy-embedment (conventional contrasting). ICG—speckle, HR—heterochromatin, Nl—nucleolus. Republished from [53]. (c) The representative image of the circular-radial self-organization of F-actin filaments (stained by phalloidin) of human foreskin fibroblasts, structured soon after seeding on isotropic substrate; from [108]. (d) Schematic of the functional transcriptional relay in its relationship with speckles and the concentric rings of the nucleolar and perinuclear heterochromatin shells, deduced from experiments with suppression of RNA synthesis and the literature on the participation of the nuclear cytoskeleton in it. Modified from [107].