Boundaries that demarcate structural and functional domains of chromatin

Understanding of how the eukaryotic genome is packaged into chromatin and w hat the functional consequences of this organization are has begun to emerg e recently. The concept of 'chromatin domains' - the topologically independ ent structural unit - is the basis of higher order chromatin organization. The idea that this structural unit may also coincide with the functional un it, offers a useful framework in dissecting the structure-function relation ship. Boundaries that define these domains have been identified and several assays have been developed to test them in vivo. We have used genetic mean s to identify and analyse such boundary elements in the bithorax complex of Drosophila melanogaster. In this review we discuss chromatin domain bounda ries identified in several systems using different means. Although there is no significant sequence conservation among various chromatin domain bounda ries, these elements show functional conservation across the species. Final ly, we discuss mechanistic aspects of how chromatin domain boundaries may f unction in organizing and regulating eukaryotic genome.