Fishwick, K. M. | bioRxiv Science

bioRxiv2025

USP7 deubiquitinase stabilizes FAN1 to support DNA crosslink repair and suppress CAG repeat expansion

Human FAN1 is a structure-specific endonuclease critical for the repair of DNA interstrand crosslinks (ICLs) and the excision of extrahelical CAG repeats-whose pathological expansion underlies Huntingtons disease (HD), a progressive and currently incurable neurodegenerative disorder. However, mechanisms of post-translational regulation of FAN1 are still largely unknown. Here, we identify the ubiquitin-specific protease 7 (USP7) as new interactor of FAN1. USP7 stabilizes FAN1 protein levels in a deubiquitination-dependent manner, preventing FAN1 from proteasomal degradation. Consequently, we demonstrate that USP7 depletion leads to reduced chromatin association of FAN1 and increased cellular hypersensitivity following ICL damage. Moreover, we find that loss of USP7 accelerates CAG repeat expansion in an HD cellular model. Collectively, our findings establish USP7 as a critical regulator of FAN1 activity in the maintenance of genome stability, highlighting potential therapeutic opportunities for cancer and HD.

molecular biology↗

bioRxiv2020

RAS-inhibiting biologics identify and probe druggable pockets including an SII-α3 allosteric site.

RAS mutations are the most common oncogenic drivers across human cancers, but there remains a paucity of clinically-validated pharmacological inhibitors of RAS, as druggable pockets have proven difficult to identify. We have identified two RAS-binding Affimer proteins, K3 and K6, that inhibit nucleotide exchange and downstream signalling pathways with distinct isoform and mutant profiles. Affimer K6 is the first biologic to bind in the SI/SII pocket, whilst Affimer K3 is the first non-covalent inhibitor of the SII region, revealing a novel RAS conformer with a large, druggable SII/3 pocket. This work demonstrates the potential of using biologics with small interface surfaces to select novel druggable conformations in conjunction with pharmacophore identification for hard-to-drug proteins.

molecular biology↗