Spontaneous emergence of sequence-dependent rosettelike folding of chromatin fiber.

In the crowded environment of the eukaryotic nucleus, the presence of intrinsic structural defects is shown to predispose chromatin fiber to spontaneously form rosettelike structures. These multilooped patterns self-organize through entropy-driven clustering of sequence-induced fiber defects by depletive forces prior to any external factors coming into play. They provide an attractive description of replication foci that are observed in interphase mammalian nuclei as stable chromatin domains of autonomous DNA replication and gene expression. Experimental perspectives for in vivo visualization of rosettelike organization of the chromatin fiber via the clustering of recently identified putative replication initiation zones are discussed.