Abstract
The tridimensional folding of the chromatin fiber results in the differential positioning of genes not only inside the cell nucleus, but also relative to each other. A combination of high resolution microscopy techniques and genome-wide analyses has uncovered the first rules that govern the spatial organization of chromatin.
This organization appears to be dictated by the primary sequence (gene density), the chemical nature of the nucleosomes and the many interactions that occur between chromatin and the molecular complexes involved in gene expression. Here we review the role that the 3D organization of chromatin plays in gene regulation.