DNA twist at the epigenome

Abstract

The ultimate step in the regulation of most genetic processes is to promote the unwinding of the DNA double helix, which is severely determined by its helical tension. However, the mechanistic links between the topology of DNA and the many other epigenetic landmarks commonly investigated are poorly understood, and even ignored for diverse reasons. On the one side, whereas massive analyses of the composition and biochemical modifications of chromatin are routinely conducted, the associated helical state of DNA is less amenable to inspect. On the other side, some classic assumptions on DNA topoisomerase function, nucleosome dynamics and chromosome architecture are misleading. Recent studies had revived the relevance of DNA topology in chromatin biology. Important emerging topics are: 1) The conformational dynamics of nucleosome and nucleosome-like structures to constrain and release DNA helical tension; 2) The distinct roles of topoisomerase I and topoisomerase II to modulate nucleosomal DNA topology; 3) The role chromatin architecture and its visco-elastic properties to constrain twist in micro and macro DNA domains.