Chromosomal architecture

During the cell cycle, chromosome structures shuttle between de-condensed interphase and condensed mitosis states. Dynamic changes also occur at the lower levels of architectures, i.e., at the chromatin and nucleosome levels. Upon gene activation and inactivation, folding and unfolding of the nucleosome structure and the chromatin fibers occur at limited loci of the genome. Namely, the structures of the chromosome are dynamic and mobile. Nevertheless, there are basic structural units that remain stable and constitute the fundamental chromosome architecture. 

A Number of Proteins are Involved in Establishing the Chromosome Architecture... 

NON-CHROMOSOMAL ARCHITECTURES SUPPORTING CHROMOSOME ARRANGEMENT IN THE NUCLEUS... 

Olins DE, Olins AL (1972) Physical studies of isolated eucaryotic nuclei. J Cell Biol 53 715-736 Ono T, Losada A, Hirano M, Myers MP, Neuwald AF, Hirano T (2003) Differential contributions of condensin I and condensin II to mitotic chromosome architecture in vertebrate cells. Cell 115 109-121... 

Ito T (2003) Nucleosome assembly and remodehng. Curr Top Microbiol Immunol 274 1-22 Ito T, Tyler JK, Kadonaga JT (1997) Chromatin assembly factors a dual function in nucleosome formation and mobilization Genes Cells 2(10) 593-600 Ivanovska I, Khandan T, Ito T, Orr-Weaver TL (2005) A histone code in meiosis the histone kinase, NHK-1, is required for proper chromosomal architecture in Drosophila oocytes. Genes Dev 19(21) 2571-2582... 

Inclusion of formamide is essential for lowering the melting temperature of DNA. It is necessary to perform denaturation and hybridization of probe and chromosomal DNA at a lower temperature to ensure preservation of chromosomal architecture. Similarly, inclusion of formamide in the stringency washes increases the stringency without having to increase the temperature... 

Ono T, et al. Differential contributions of condensin I and condensin II to mitotic chromosome architecture in vertebrate cells. Cell 2003 115 109-121. 

Many compounds can lead to cancer via non-genotoxic mechanisms, rendering the evaluation and assessment of their toxic potential rather complex. The primary action of these compounds is not DNA reactivity they do not directly interact to alter chromosome architecture or number furthermore, genotoxic events... 

Mapping Three-Dimensional Chromosome Architecture in Situ... 

Heck MM. 1997. Condensins, cohesins, and chromosome architecture how to make and break a mitotic chromosome. Cell 91(l) 5-8. 

Since a recombination event between two loxP sites some distance apart or positioned on different chromosomes, is relatively rare, presumably because of physical constraints, a reflection of chromosome architecture and decreased proximity, such strategies are designed incorporating a binary positive selection system that is only activated after a successful recombination recreates the cassette. Thus, the desired recombination event will reconstruct the selectable genetic marker, from two silent portions placed adjacent to each of the loxP sites. The most commonly used selection systems include the reconstitution of a human hypoxanthine phosphoribosyltransferase (HPRT) minigene (16-20), or the juxtaposition of a strong promoter upstream of a selectable marker. 

The Drosophila embryo has provided an excellent model system for a variety of questions in chromosome biology, including investigations of somatic chromosome architecture and chromosome-associated proteins. Its advantages include the ease of obtaining populations of staged specimens (see Sisson, this volume), as well as a variety of techniques for experimental manipulation, fixation, and staining of specific cellular components. The... 

Dernburg A.F. and Sedat J.W. 1998. Mapping three-dimensional chromosome architecture in situ. Methods Cell Biol. 53 187-233. 

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