OVERWIEW OF THREE DIMENSIONAL GENOM ORGANIZATION

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A fundamental property of genomes is their topological organization in the cell nucleus. “Chromosome territories” refer to the use of certain regions of the nucleus by a specific chromosomes. It is determined that, chromosomes are not arranged randomly in the cell space and many genes in the genom occupy preferred areas. The organization of chromosomal domains are associated to gene density and size. In this case, it has been reported that gene-rich chromosomes prefer interior positions and that gene-poor chromosomes prefer peripheral positions. Chromosomal domains are also dynamic structures, so genes can be displaced from the periphery to the interior position when opened. It is known that the spatial organization of the human genome plays an important role in the transcriptional control of genes. Based on studies of promoter and enhancer interactions by DNA looping, it is clear that gene expression is facilitated and regulated through contacts of distal chromatin contacts. The primary research topics are how regulatory DNA elements and genes are wired to properly execute cell-specific transcription regulatory programs. Genetic experiments have uncovered three rules of enhancer–promoter engagement: linear proximity matters, enhancer and promoter compatibility and some sequences exist that can block enhancer activity. To understand the molecular mechanisms behind these rules, we need to know how regulatory sites exert activities over distance. It is found that a given mammalian cell type contains thousands or more regulatory sites. With 200 different cell types, this confirms that our genome harbours a complex regulatory landscape. From linear DNA to the three dimensional nucleus, chromatin organization is well characterized on both the small scale and the very large scale; however, our understanding of the intermediate levels of chromatin organization remains limited. With the advent of chromosome conformation capture (3C) technologies tremendous progress in our understanding of three dimensional chromatin organization of interphase nucleus has been made. In this review, it is mentioned about spatial organization of genom, some interactions in this organisation and some actual studies in recent years.

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Three dimensional genome , Chromosome territories , Enhancer , Insulator , Topological domains

Kocatepe Medical Journal

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Kocatepe Medical Journal