Nuclear dynamics of topoisomerase IIβ 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 IIβ tagged with EGFP. Activity attenuation experiments and nuclear localization data reveal that the endogenous activity of topo IIβ 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 IIβ 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 IIβ are mediated by the interplay between cellular RNA and the CRD.

Dynamic behavior of DNA topoisomerase IIβ in response to DNA double-strand breaks

“…Both proteins in the undamaged nucleoplasm were washed out by detergent treatment, supporting the tight association of endogenous Topo IIβ with damaged sites. In several detergent-treated cells, Topo IIβ resided in the nucleoli, presumably because alterations in cellular energy status arose during detergent treatment and consequently caused stable accumulation of Topo IIβ therein as previously reported 32 .…”

DNA topoisomerase IIβ stimulates neurite outgrowth in neural differentiated human mesenchymal stem cells through regulation of Rho-GTPases (RhoA/Rock2 pathway) and Nurr1 expression

“…It has been shown that nuclear localization of topo IIβ is highly correlated with its catalytic activity. Active topo IIβ is largely nucleoplasmic, while the nucleolar form is inactive [ 42 ]. It is possible that there could be a link between the subcellular localization of RhoA and its activity.…”

TOP2B: The First Thirty Years

“…Studies with antisera raised to TOP2B CTD and using TOP2B CTD galactosidase tagged constructs in HeLa and monkey COS7 cells showed nucleoplasmic staining with no evidence for significant nucleolar enrichment [ 114 ]. Onoda et al, 2014 [ 115 ] show shuttling of TOP2B between the nucleolus and the nucleoplasm, and suggest that the enzyme is active when in the nucleoplasm. Cowell et al, 2011 demonstrated that Top2b is enriched in heterochromatic regions in mouse epithelial cells and relocates to give a pan nuclear staining upon treatment with the histone deacetylase inhibitor TSA [ 116 ], treatment which also causes loss of HP1 from heterochromatin [ 117 ].…”