Dynamic chromatin organization without the 30-nm fiber.

Chromatin in eukaryotic cells is a negatively charged polymer composed of DNA, histones, and various associated proteins. Over the past ten years, our view of chromatin has shifted from a static regular structure to a dynamic and highly variable configuration. While the details are not fully understood yet, chromatin forms numerous compact domains that act as dynamic functional units of the genome in higher eukaryotes. By altering DNA accessibility, the dynamic nature of chromatin governs various genome functions including RNA transcription, DNA replication, and DNA repair/recombination. Based on the new evidence coming from both genomics and imaging studies, we discuss the structural and dynamic aspects of chromatin and their biological relevance in the living cell.