Topoisomerase II in the Inactive X Chromosome as Determined by Immunofluorescence

Abstract

Topoisomerases are enzymes that convert DNA from one topological state to another. A particular type of topoisomerase, type II, appears also to be a member of the chromosome scaffold, bound to the base of radial DNA loops. Using immunofluorescence coupled with DNase digestions, we determined an association between the topoisomerase II and the sex chromatin body. Based upon this association, we postulate that topoisomerase II may be involved in the compartmentalization of the sex chromatin body. Since no topoisomerase II has been detected in the G-] phase of the cell cycle, topoisomerase II must act with other, yet to be determined proteins in order to maintain the compartmentalization of the sex chromatin body throughout the cell cycle.