Limits...
Chromosome Architecture and Genome Organization.

Bernardi G - PLoS ONE (2015)

Bottom Line: This is a critical range that encompasses isochores, interphase chromatin domains and boundaries, and chromosomal bands.The solution rests on the following key points: 1) the transition from the looped domains and sub-domains of interphase chromatin to the 30-nm fiber loops of early prophase chromosomes goes through the unfolding into an extended chromatin structure (probably a 10-nm "beads-on-a-string" structure); 2) the architectural proteins of interphase chromatin, such as CTCF and cohesin sub-units, are retained in mitosis and are part of the discontinuous protein scaffold of mitotic chromosomes; 3) the conservation of the link between architectural proteins and their binding sites on DNA through the cell cycle explains the "mitotic memory" of interphase architecture and the reversibility of the interphase to mitosis process.The results presented here also lead to a general conclusion which concerns the existence of correlations between the isochore organization of the genome and the architecture of chromosomes from interphase to metaphase.

View Article: PubMed Central - PubMed

Affiliation: Science Department, Roma Tre University, Marconi, Rome, Italy.

ABSTRACT
How the same DNA sequences can function in the three-dimensional architecture of interphase nucleus, fold in the very compact structure of metaphase chromosomes and go precisely back to the original interphase architecture in the following cell cycle remains an unresolved question to this day. The strategy used to address this issue was to analyze the correlations between chromosome architecture and the compositional patterns of DNA sequences spanning a size range from a few hundreds to a few thousands Kilobases. This is a critical range that encompasses isochores, interphase chromatin domains and boundaries, and chromosomal bands. The solution rests on the following key points: 1) the transition from the looped domains and sub-domains of interphase chromatin to the 30-nm fiber loops of early prophase chromosomes goes through the unfolding into an extended chromatin structure (probably a 10-nm "beads-on-a-string" structure); 2) the architectural proteins of interphase chromatin, such as CTCF and cohesin sub-units, are retained in mitosis and are part of the discontinuous protein scaffold of mitotic chromosomes; 3) the conservation of the link between architectural proteins and their binding sites on DNA through the cell cycle explains the "mitotic memory" of interphase architecture and the reversibility of the interphase to mitosis process. The results presented here also lead to a general conclusion which concerns the existence of correlations between the isochore organization of the genome and the architecture of chromosomes from interphase to metaphase.

Show MeSH
The banding pattern of chromosome 21: (A), at early prophase, (B), at prometaphase and (C) at metaphase. Vertical lines connect early prophase bands formed by single isochores (marked by red asterisks) or isochore blocks (the macroisochores) with prometaphase bands. B→C. The following coalescence process leads to different ratios of prometaphase to metaphase bands, 1:1, 3:1, 5:1. A’ B’ C’. The compositional profiles A’ of isochores (early prophase); B’ macroisochores (prometaphase) and C’ megaisochores (metaphase). D, E. GC levels of prometaphase (D) and metaphase (E) bands.Blue and red points indicate G and R bands. Red arrows and asterisks indicate single-isochore bands. The red horizontal line separates the two genome compartments, GC-poor and GC-rich.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4664426&req=5

pone.0143739.g004: The banding pattern of chromosome 21: (A), at early prophase, (B), at prometaphase and (C) at metaphase. Vertical lines connect early prophase bands formed by single isochores (marked by red asterisks) or isochore blocks (the macroisochores) with prometaphase bands. B→C. The following coalescence process leads to different ratios of prometaphase to metaphase bands, 1:1, 3:1, 5:1. A’ B’ C’. The compositional profiles A’ of isochores (early prophase); B’ macroisochores (prometaphase) and C’ megaisochores (metaphase). D, E. GC levels of prometaphase (D) and metaphase (E) bands.Blue and red points indicate G and R bands. Red arrows and asterisks indicate single-isochore bands. The red horizontal line separates the two genome compartments, GC-poor and GC-rich.

Mentions: Fig 4A and 4B shows the transition, in chromosome 21, from early prophase bands to prometaphase bands. In two cases (bands q21.2 and q22.11), prometaphase bands correspond to single isochores, in all other cases to multiple contiguous isochores, to isochore blocks (the macroisochores). At prometaphase, multiple-isochore bands represent 75% of all bands (see Fig 3).


Chromosome Architecture and Genome Organization.

Bernardi G - PLoS ONE (2015)

The banding pattern of chromosome 21: (A), at early prophase, (B), at prometaphase and (C) at metaphase. Vertical lines connect early prophase bands formed by single isochores (marked by red asterisks) or isochore blocks (the macroisochores) with prometaphase bands. B→C. The following coalescence process leads to different ratios of prometaphase to metaphase bands, 1:1, 3:1, 5:1. A’ B’ C’. The compositional profiles A’ of isochores (early prophase); B’ macroisochores (prometaphase) and C’ megaisochores (metaphase). D, E. GC levels of prometaphase (D) and metaphase (E) bands.Blue and red points indicate G and R bands. Red arrows and asterisks indicate single-isochore bands. The red horizontal line separates the two genome compartments, GC-poor and GC-rich.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4664426&req=5

pone.0143739.g004: The banding pattern of chromosome 21: (A), at early prophase, (B), at prometaphase and (C) at metaphase. Vertical lines connect early prophase bands formed by single isochores (marked by red asterisks) or isochore blocks (the macroisochores) with prometaphase bands. B→C. The following coalescence process leads to different ratios of prometaphase to metaphase bands, 1:1, 3:1, 5:1. A’ B’ C’. The compositional profiles A’ of isochores (early prophase); B’ macroisochores (prometaphase) and C’ megaisochores (metaphase). D, E. GC levels of prometaphase (D) and metaphase (E) bands.Blue and red points indicate G and R bands. Red arrows and asterisks indicate single-isochore bands. The red horizontal line separates the two genome compartments, GC-poor and GC-rich.
Mentions: Fig 4A and 4B shows the transition, in chromosome 21, from early prophase bands to prometaphase bands. In two cases (bands q21.2 and q22.11), prometaphase bands correspond to single isochores, in all other cases to multiple contiguous isochores, to isochore blocks (the macroisochores). At prometaphase, multiple-isochore bands represent 75% of all bands (see Fig 3).

Bottom Line: This is a critical range that encompasses isochores, interphase chromatin domains and boundaries, and chromosomal bands.The solution rests on the following key points: 1) the transition from the looped domains and sub-domains of interphase chromatin to the 30-nm fiber loops of early prophase chromosomes goes through the unfolding into an extended chromatin structure (probably a 10-nm "beads-on-a-string" structure); 2) the architectural proteins of interphase chromatin, such as CTCF and cohesin sub-units, are retained in mitosis and are part of the discontinuous protein scaffold of mitotic chromosomes; 3) the conservation of the link between architectural proteins and their binding sites on DNA through the cell cycle explains the "mitotic memory" of interphase architecture and the reversibility of the interphase to mitosis process.The results presented here also lead to a general conclusion which concerns the existence of correlations between the isochore organization of the genome and the architecture of chromosomes from interphase to metaphase.

View Article: PubMed Central - PubMed

Affiliation: Science Department, Roma Tre University, Marconi, Rome, Italy.

ABSTRACT
How the same DNA sequences can function in the three-dimensional architecture of interphase nucleus, fold in the very compact structure of metaphase chromosomes and go precisely back to the original interphase architecture in the following cell cycle remains an unresolved question to this day. The strategy used to address this issue was to analyze the correlations between chromosome architecture and the compositional patterns of DNA sequences spanning a size range from a few hundreds to a few thousands Kilobases. This is a critical range that encompasses isochores, interphase chromatin domains and boundaries, and chromosomal bands. The solution rests on the following key points: 1) the transition from the looped domains and sub-domains of interphase chromatin to the 30-nm fiber loops of early prophase chromosomes goes through the unfolding into an extended chromatin structure (probably a 10-nm "beads-on-a-string" structure); 2) the architectural proteins of interphase chromatin, such as CTCF and cohesin sub-units, are retained in mitosis and are part of the discontinuous protein scaffold of mitotic chromosomes; 3) the conservation of the link between architectural proteins and their binding sites on DNA through the cell cycle explains the "mitotic memory" of interphase architecture and the reversibility of the interphase to mitosis process. The results presented here also lead to a general conclusion which concerns the existence of correlations between the isochore organization of the genome and the architecture of chromosomes from interphase to metaphase.

Show MeSH