SPRTN patient variants cause global-genome DNA-protein crosslink repair defects.

DNA-protein crosslinks (DPCs) are pervasive DNA lesions that are induced by reactive metabolites and various chemotherapeutic agents. Here, we develop a technique for the Purification of x-linked Proteins (PxP), which allows identification and tracking of diverse DPCs in mammalian cells. Using PxP, we investigate DPC repair in cells genetically-engineered to express variants of the SPRTN protease that cause premature ageing and early-onset liver cancer in Ruijs-Aalfs syndrome patients.

A ubiquitin switch controls autocatalytic inactivation of the DNA-protein crosslink repair protease SPRTN.

Repair of covalent DNA-protein crosslinks (DPCs) by the metalloprotease SPRTN prevents genome instability, premature aging and carcinogenesis. SPRTN is specifically activated by DNA structures containing single- and double-stranded features, but degrades the protein components of DPCs promiscuously and independent of amino acid sequence. This lack of specificity is useful to target diverse protein adducts, however, it requires tight control in return, in order to prohibit uncontrolled proteolysis of chromatin proteins.

DNA Structure-Specific Cleavage of DNA-Protein Crosslinks by the SPRTN Protease.

Repair of covalent DNA-protein crosslinks (DPCs) by DNA-dependent proteases has emerged as an essential genome maintenance mechanism required for cellular viability and tumor suppression. However, how proteolysis is restricted to the crosslinked protein while leaving surrounding chromatin proteins unharmed has remained unknown. Using defined DPC model substrates, we show that the DPC protease SPRTN displays strict DNA structure-specific activity.