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Chromosome Scaffold is a Double-Stranded Assembly of Scaffold Proteins.

Poonperm R, Takata H, Hamano T, Matsuda A, Uchiyama S, Hiraoka Y, Fukui K - Sci Rep (2015)

Bottom Line: This reversion to the original morphology underscores the role of the scaffold for intrinsic structural integrity of chromosomes.We therefore propose a new structural model of the chromosome scaffold that includes twisted double strands, consistent with the physical properties of chromosomal bending flexibility and rigidity.Our model provides new insights into chromosome higher order structure.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, JAPAN.

ABSTRACT
Chromosome higher order structure has been an enigma for over a century. The most important structural finding has been the presence of a chromosome scaffold composed of non-histone proteins; so-called scaffold proteins. However, the organization and function of the scaffold are still controversial. Here, we use three dimensional-structured illumination microscopy (3D-SIM) and focused ion beam/scanning electron microscopy (FIB/SEM) to reveal the axial distributions of scaffold proteins in metaphase chromosomes comprising two strands. We also find that scaffold protein can adaptably recover its original localization after chromosome reversion in the presence of cations. This reversion to the original morphology underscores the role of the scaffold for intrinsic structural integrity of chromosomes. We therefore propose a new structural model of the chromosome scaffold that includes twisted double strands, consistent with the physical properties of chromosomal bending flexibility and rigidity. Our model provides new insights into chromosome higher order structure.

No MeSH data available.


Related in: MedlinePlus

The double-stranded chromosome scaffold (DCS) is highly adaptable in relation to chromosome changes.a, Maximum intensity projections of z-stack images obtained by 3D-SIM of unfixed PA chromosome treated with PBS (Control), 1 mM EDTA (Expansion), or H-Mg (Reversion). Scale bar, 2 μm. Arrowheads indicate double strands. Asterisks indicate the centromeric region. Insets show magnified views of white boxes. Scale bar, 250 nm. b, Relative chromosome or chromosome scaffold length and width in each treatment. Bar denotes the mean; NS, not significant; error bar denotes standard deviation (n = 46). c, Schematic chromosome scaffold adaptations in relation to scaffold protein interactions and chromatin network reinforcement.
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f4: The double-stranded chromosome scaffold (DCS) is highly adaptable in relation to chromosome changes.a, Maximum intensity projections of z-stack images obtained by 3D-SIM of unfixed PA chromosome treated with PBS (Control), 1 mM EDTA (Expansion), or H-Mg (Reversion). Scale bar, 2 μm. Arrowheads indicate double strands. Asterisks indicate the centromeric region. Insets show magnified views of white boxes. Scale bar, 250 nm. b, Relative chromosome or chromosome scaffold length and width in each treatment. Bar denotes the mean; NS, not significant; error bar denotes standard deviation (n = 46). c, Schematic chromosome scaffold adaptations in relation to scaffold protein interactions and chromatin network reinforcement.

Mentions: To examine the adaptability of the DCS in chromosome condensation and decondensation, we tracked the distribution of hCAP-E in unfixed PA chromosomes after removal and subsequent re-addition of Mg2+ for induction of chromosome decondensation and recondensation, respectively1819. Initially, unfixed PA chromosomes maintained in PBS exhibited an authentic morphology and the hCAP-E distribution was visualized as double-stranded (Fig. 4a, Control), similar to that in fixed chromosomes (Fig. 1b,c). After substitution of PBS with 1 mM EDTA, chromosomes were swollen due to lack of Mg2+ (Fig. 4a, Expansion). At this stage, hCAP-E signals were still axially located in the chromatids, but the distribution pattern broadened and lengthened in parallel with expansion of chromosome width and length (Fig. 4a, Expansion). After exchange of 1 mM EDTA with HEPES-buffer containing 5 mM Mg2+ (H-Mg), authentic chromosome morphology was recovered and hCAP-E localization was restored (Fig. 4a, Reversion). Interestingly, at the centromeric positions, no distribution change of hCAP-E was observed, and hCAP-E fluorescence signals remained strong (Fig. 4a, bottom panel) in all conditions. These results show that chromosome scaffold organization is adaptable to different chromosome states: a broken, discontinuous organization in the expanded state versus a twisted double-strand in the compacted state (Fig. 4a). Chromosomes are, therefore, able to change its morphology reversibly and adaptably to their physiological conditions. This is consistent with micromechanical measurement results showing that chromosomes are flexible objects920.


Chromosome Scaffold is a Double-Stranded Assembly of Scaffold Proteins.

Poonperm R, Takata H, Hamano T, Matsuda A, Uchiyama S, Hiraoka Y, Fukui K - Sci Rep (2015)

The double-stranded chromosome scaffold (DCS) is highly adaptable in relation to chromosome changes.a, Maximum intensity projections of z-stack images obtained by 3D-SIM of unfixed PA chromosome treated with PBS (Control), 1 mM EDTA (Expansion), or H-Mg (Reversion). Scale bar, 2 μm. Arrowheads indicate double strands. Asterisks indicate the centromeric region. Insets show magnified views of white boxes. Scale bar, 250 nm. b, Relative chromosome or chromosome scaffold length and width in each treatment. Bar denotes the mean; NS, not significant; error bar denotes standard deviation (n = 46). c, Schematic chromosome scaffold adaptations in relation to scaffold protein interactions and chromatin network reinforcement.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4487240&req=5

f4: The double-stranded chromosome scaffold (DCS) is highly adaptable in relation to chromosome changes.a, Maximum intensity projections of z-stack images obtained by 3D-SIM of unfixed PA chromosome treated with PBS (Control), 1 mM EDTA (Expansion), or H-Mg (Reversion). Scale bar, 2 μm. Arrowheads indicate double strands. Asterisks indicate the centromeric region. Insets show magnified views of white boxes. Scale bar, 250 nm. b, Relative chromosome or chromosome scaffold length and width in each treatment. Bar denotes the mean; NS, not significant; error bar denotes standard deviation (n = 46). c, Schematic chromosome scaffold adaptations in relation to scaffold protein interactions and chromatin network reinforcement.
Mentions: To examine the adaptability of the DCS in chromosome condensation and decondensation, we tracked the distribution of hCAP-E in unfixed PA chromosomes after removal and subsequent re-addition of Mg2+ for induction of chromosome decondensation and recondensation, respectively1819. Initially, unfixed PA chromosomes maintained in PBS exhibited an authentic morphology and the hCAP-E distribution was visualized as double-stranded (Fig. 4a, Control), similar to that in fixed chromosomes (Fig. 1b,c). After substitution of PBS with 1 mM EDTA, chromosomes were swollen due to lack of Mg2+ (Fig. 4a, Expansion). At this stage, hCAP-E signals were still axially located in the chromatids, but the distribution pattern broadened and lengthened in parallel with expansion of chromosome width and length (Fig. 4a, Expansion). After exchange of 1 mM EDTA with HEPES-buffer containing 5 mM Mg2+ (H-Mg), authentic chromosome morphology was recovered and hCAP-E localization was restored (Fig. 4a, Reversion). Interestingly, at the centromeric positions, no distribution change of hCAP-E was observed, and hCAP-E fluorescence signals remained strong (Fig. 4a, bottom panel) in all conditions. These results show that chromosome scaffold organization is adaptable to different chromosome states: a broken, discontinuous organization in the expanded state versus a twisted double-strand in the compacted state (Fig. 4a). Chromosomes are, therefore, able to change its morphology reversibly and adaptably to their physiological conditions. This is consistent with micromechanical measurement results showing that chromosomes are flexible objects920.

Bottom Line: This reversion to the original morphology underscores the role of the scaffold for intrinsic structural integrity of chromosomes.We therefore propose a new structural model of the chromosome scaffold that includes twisted double strands, consistent with the physical properties of chromosomal bending flexibility and rigidity.Our model provides new insights into chromosome higher order structure.

View Article: PubMed Central - PubMed

Affiliation: Department of Biotechnology, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, JAPAN.

ABSTRACT
Chromosome higher order structure has been an enigma for over a century. The most important structural finding has been the presence of a chromosome scaffold composed of non-histone proteins; so-called scaffold proteins. However, the organization and function of the scaffold are still controversial. Here, we use three dimensional-structured illumination microscopy (3D-SIM) and focused ion beam/scanning electron microscopy (FIB/SEM) to reveal the axial distributions of scaffold proteins in metaphase chromosomes comprising two strands. We also find that scaffold protein can adaptably recover its original localization after chromosome reversion in the presence of cations. This reversion to the original morphology underscores the role of the scaffold for intrinsic structural integrity of chromosomes. We therefore propose a new structural model of the chromosome scaffold that includes twisted double strands, consistent with the physical properties of chromosomal bending flexibility and rigidity. Our model provides new insights into chromosome higher order structure.

No MeSH data available.


Related in: MedlinePlus