Nuclear dynamics of topoisomerase II? reflects its catalytic activity that is regulated by binding of RNA to the C-terminal domain.

ABSTRACT: DNA topoisomerase II (topo II) changes DNA topology by cleavage/re-ligation cycle(s) and thus contributes to various nuclear DNA transactions. It is largely unknown how the enzyme is controlled in a nuclear context. Several studies have suggested that its C-terminal domain (CTD), which is dispensable for basal relaxation activity, has some regulatory influence. In this work, we examined the impact of nuclear localization on regulation of activity in nuclei. Specifically, human cells were transfected with wild-type and mutant topo II? tagged with EGFP. Activity attenuation experiments and nuclear localization data reveal that the endogenous activity of topo II? is correlated with its subnuclear distribution. The enzyme shuttles between an active form in the nucleoplasm and a quiescent form in the nucleolus in a dynamic equilibrium. Mechanistically, the process involves a tethering event with RNA. Isolated RNA inhibits the catalytic activity of topo II? in vitro through the interaction with a specific 50-residue region of the CTD (termed the CRD). Taken together, these results suggest that both the subnuclear distribution and activity regulation of topo II? are mediated by the interplay between cellular RNA and the CRD.

SUBMITTER: Onoda A 

PROVIDER: S-EPMC4132749 | biostudies-literature | 2014 Aug

REPOSITORIES: biostudies-literature