Dynamics of passive and active particles in the cell nucleus.

Inspite of being embedded in a dense meshwork of nuclear chromatin, gene loci and large nuclear components are highly dynamic at 37°C. To understand this apparent unfettered movement in an overdense environment, we study the dynamics of a passive micron size bead in live cell nuclei at two different...

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Autores principales:	Feroz M Hameed, Madan Rao, G V Shivashankar
Formato:	article
Lenguaje:	EN
Publicado:	Public Library of Science (PLoS) 2012
Materias:	Medicine R Science Q
Acceso en línea:	https://doaj.org/article/cf21409900c14b7c861bf22b9e268201
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spelling	oai:doaj.org-article:cf21409900c14b7c861bf22b9e2682012021-11-18T08:12:07ZDynamics of passive and active particles in the cell nucleus.1932-620310.1371/journal.pone.0045843https://doaj.org/article/cf21409900c14b7c861bf22b9e2682012012-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23077497/?tool=EBIhttps://doaj.org/toc/1932-6203Inspite of being embedded in a dense meshwork of nuclear chromatin, gene loci and large nuclear components are highly dynamic at 37°C. To understand this apparent unfettered movement in an overdense environment, we study the dynamics of a passive micron size bead in live cell nuclei at two different temperatures (25 and 37°C) with and without external force. In the absence of a force, the beads are caged over large time scales. On application of a threshold uniaxial force (about 10(2) pN), the passive beads appear to hop between cages; this large scale movement is absent upon ATP-depletion, inhibition of chromatin remodeling enzymes and RNAi of lamin B1 proteins. Our results suggest that the nucleus behaves like an active solid with a finite yield stress when probed at a micron scale. Spatial analysis of histone fluorescence anisotropy (a measure of local chromatin compaction, defined as the volume fraction of tightly bound chromatin) shows that the bead movement correlates with regions of low chromatin compaction. This suggests that the physical mechanism of the observed yielding is the active opening of free-volume in the nuclear solid via chromatin remodeling. Enriched transcription sites at 25°C also show caging in the absence of the applied force and directed movement beyond a yield stress, in striking contrast with the large scale movement of transcription loci at 37°C in the absence of a force. This suggests that at physiological temperatures, the loci behave as active particles which remodel the nuclear mesh and reduce the local yield stress.Feroz M HameedMadan RaoG V ShivashankarPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 7, Iss 10, p e45843 (2012)
institution	DOAJ
collection	DOAJ
language	EN
topic	Medicine R Science Q
spellingShingle	Medicine R Science Q Feroz M Hameed Madan Rao G V Shivashankar Dynamics of passive and active particles in the cell nucleus.
description	Inspite of being embedded in a dense meshwork of nuclear chromatin, gene loci and large nuclear components are highly dynamic at 37°C. To understand this apparent unfettered movement in an overdense environment, we study the dynamics of a passive micron size bead in live cell nuclei at two different temperatures (25 and 37°C) with and without external force. In the absence of a force, the beads are caged over large time scales. On application of a threshold uniaxial force (about 10(2) pN), the passive beads appear to hop between cages; this large scale movement is absent upon ATP-depletion, inhibition of chromatin remodeling enzymes and RNAi of lamin B1 proteins. Our results suggest that the nucleus behaves like an active solid with a finite yield stress when probed at a micron scale. Spatial analysis of histone fluorescence anisotropy (a measure of local chromatin compaction, defined as the volume fraction of tightly bound chromatin) shows that the bead movement correlates with regions of low chromatin compaction. This suggests that the physical mechanism of the observed yielding is the active opening of free-volume in the nuclear solid via chromatin remodeling. Enriched transcription sites at 25°C also show caging in the absence of the applied force and directed movement beyond a yield stress, in striking contrast with the large scale movement of transcription loci at 37°C in the absence of a force. This suggests that at physiological temperatures, the loci behave as active particles which remodel the nuclear mesh and reduce the local yield stress.
format	article
author	Feroz M Hameed Madan Rao G V Shivashankar
author_facet	Feroz M Hameed Madan Rao G V Shivashankar
author_sort	Feroz M Hameed
title	Dynamics of passive and active particles in the cell nucleus.
title_short	Dynamics of passive and active particles in the cell nucleus.
title_full	Dynamics of passive and active particles in the cell nucleus.
title_fullStr	Dynamics of passive and active particles in the cell nucleus.
title_full_unstemmed	Dynamics of passive and active particles in the cell nucleus.
title_sort	dynamics of passive and active particles in the cell nucleus.
publisher	Public Library of Science (PLoS)
publishDate	2012
url	https://doaj.org/article/cf21409900c14b7c861bf22b9e268201
work_keys_str_mv	AT ferozmhameed dynamicsofpassiveandactiveparticlesinthecellnucleus AT madanrao dynamicsofpassiveandactiveparticlesinthecellnucleus AT gvshivashankar dynamicsofpassiveandactiveparticlesinthecellnucleus
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Dynamics of passive and active particles in the cell nucleus.

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