Dual-utility NLS Drives RNF169-dependent DNA Damage Responses

Abstract

Loading of 53BP1 and RAP80 at DNA double-strand breaks (DSBs) drives cell cycle checkpoint activation but is counterproductive to high-fidelity DNA repair. RNF169 maintains the balance by limiting the deposition of DNA damage mediator proteins at the damaged chromatin. We report here that this is accomplished, in part, by a predicted NLS that not only shuttles RNF169 into the nucleus, but also promotes its stability by mediating a direct interaction with the ubiquitin specific protease USP7. Guided by the crystal structure of USP7 in complex with the RNF169 NLS, we uncoupled USP7 binding from its nuclear import function, and showed that perturbing the USP7-RNF169 complex destabilized RNF169, compromised high-fidelity DSB repair, and hyper-sensitized cells to PARP inhibition. Finally, expression of USP7 and RNF169 positively correlated in breast cancer specimens. Collectively, our findings uncover an NLS-mediated bipartite mechanism that supports the nuclear function of a DSB response protein.