Protein-protein interactions regulate many essential enzymatic processes in the cell. Somatic mutations outside of an enzyme active site can therefore impact cellular function by disruption of critical protein-protein interactions. In our investigation of the cellular impact of the T304I cancer mutation of DNA Polymerase β (Polβ), we find that mutation of this surface threonine residue impacts critical Polβ protein-protein interactions. We show that proteasome-mediated degradation of Polβ is regulated by both ubiquitin-dependent and ubiquitin-independent processes via unique protein-protein interactions. The ubiquitin-independent proteasome pathway regulates the stability of Polβ in the cytosol via interaction between Polβ and NAD(P)H quinone dehydrogenase 1 (NQO1) in an NADH-dependent manner. Conversely, the interaction of Polβ with the scaffold protein X-ray repair cross complementing 1 (XRCC1) plays a role in the localization of Polβ to the nuclear compartment and regulates the stability of Polβ via a ubiquitin-dependent pathway. Further, we find that oxidative stress promotes the dissociation of the Polβ/NQO1 complex, enhancing the interaction of Polβ with XRCC1. Our results reveal that somatic mutations such as T304I in Polβ impact critical protein-protein interactions, altering the stability and sub-cellular localization of Polβ and providing mechanistic insight into how key protein-protein interactions regulate cellular responses to stress.

Additional Metadata
Persistent URL dx.doi.org/10.1093/nar/gkz293, hdl.handle.net/1765/118345
Journal Nucleic Acids Research
Citation
Fang, Q. (Qingming), Andrews, J. (Joel), Sharma, N. (Nidhi), Wilk, A. (Anna), Clark, J. (Jennifer), Slyskova, J. (Jana), … Sobol, R.W. (2019). Stability and sub-cellular localization of DNA polymerase β is regulated by interactions with NQO1 and XRCC1 in response to oxidative stress. Nucleic Acids Research, 47(12), 6269–6286. doi:10.1093/nar/gkz293