Rapid chromosome territory relocation by nuclear motor activity in response to serum removal in primary human fibroblasts

Mehta, Amira Manelle, Harvey, Bridger

Description

Radial chromosome positioning in interphase nuclei is nonrandom and can alter according to developmental, differentiation, proliferation, or disease status. However, it is not yet clear when and how chromosome repositioning is elicited. Results By investigating the positioning of all human chromosomes in primary fibroblasts that have left the proliferative cell cycle, we have demonstrated that in cells made quiescent by reversible growth arrest, chromosome positioning is altered considerably. We found that with the removal of serum from the culture medium, chromosome repositioning took less than 15 minutes, required energy and was inhibited by drugs affecting the polymerization of myosin and actin. We also observed that when cells became quiescent, the nuclear distribution of nuclear myosin 1β was dramatically different from that in proliferating cells. If we suppressed the expression of nuclear myosin 1β by using RNA-interference procedures, the movement of chromosomes after 15 minutes in low serum was inhibited. When high serum was restored to the serum-starved cultures, chromosome repositioning was evident only after 24 to 36 hours, and this coincided with a return to a proliferating distribution of nuclear myosin 1β. Conclusions These findings demonstrate that genome organization in interphase nuclei is altered considerably when cells leave the proliferative cell cycle and that repositioning of chromosomes relies on efficient functioning of an active nuclear motor complex that contains nuclear myosin 1β.

Informations

• Publié par: biomed
• Publié le: 01 janvier 2010
• Nombre de lectures: 6
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Mehtaet al.Genome Biology2010,11:R5 http://genomebiology.com/2010/11/1/R5

R E S E A R C H Open Access Research Rapid chromosome territory relocation by nuclear motor activity in response to serum removal in primary human fibroblasts

1,2 21 Ishita S Mehta1, Manelle Amira, Amanda J Harveyand Joanna M Bridger*

Background Within interphase nuclei, individual chromosomes are organized within their own nuclear space, known as chromosome territories [1,2]. These interphase chromo- some territories are organized in a nonrandom manner in the nuclei of human cells and cells from other species [3]. Chromosomes in different species are positioned radially, according to either their gene density [4-9] or their size [10-12] or both [11,13-16]. The nuclear microenviron- ment within which a chromosome is located could affect its gene regulation, and it has been proposed that whole chromosomes or regions of chromosomes are shifted around the nucleus to control gene expression [17,18]. Active genes appear to come together in a common nuclear space, possibly to be co-transcribed [19-21]. This

* Correspondence: [e-mail] 1 Centre for Cell and Chromosome Biology, Division of Biosciences, School of Health Sciences and Social Care, Brunel University, Kingston Lane, Uxbridge, UB8 3PH, UK

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fits with the increasing number of observations made of chromosome loops, containing active areas of the genome, coming away from the main body of the chro- mosome territory, such as regions containingFLNAon the X chromosome [22]; major histocompatibility com- plex (MHC) genes [23], specific genes on chromosome 11 [24]; β- globin-like genes [25], epidermal differentiation complex genes [26], specific genes within theHox Bclus- ter [27,28], and genes inducing porcine stem cell differen- tiation into adipocytes [29]. Chromatin looping is apparently associated with gene expression, because inhi- bition of RNA polymerase II transcription affects the out- ward movement of these chromosome loops [30]. Repositioning of whole chromosome territories has been observed in erythroid differentiation [25], adipo- genesis [31], T-cell differentiation [32], porcine sper- matogenesis [33], and after hormonal stimulus [34]. Even more studies revealed genomic loci being repositioned during differentiation (see [35], for comprehensive

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