ACRC/GCNA is an essential protease that repairs DNA-protein crosslinks during vertebrate development

DNA-protein crosslinks (DPCs) are toxic DNA lesions that block all DNA transactions including replication and transcription, and the consequences of impaired DNA-Protein Crosslink Repair (DPCR) are severe. At the cellular level, impaired DPCR leads to the formation of double strand breaks, genomic instability and cell death, while at the organismal level, it is associated with cancer, aging and neurodegeneration. Despite its importance, the mechanisms of DPCR at the organismal level are largely unknown. Proteases play a central role in DPCR, as they remove proteinaceous part of the DPCs, while the peptide remnant crosslinked to DNA is subsequently removed by other repair factors. We characterized the role of putative protease ACRC/GCNA (ACidic Repeat Containing/Germ Cell Nuclear Antigen) in DPCR at the organismal level. For this purpose, we have created new animal models with CRISPR/Cas system: two zebrafish lines with inactive Acrc. We were able to overcome the early embryonic lethality caused by Acrc inactivation by injecting Acrc-WT mRNA and have created a viable animal model to study the role of Acrc in adult tissues. We identified histone H3, topoisomerases 1 and 2, Dnmt1, Parp1, Polr3a and Mcm2 as DPC substrates of Acrc. We have proven that Acrc is absolutely essential for vertebrate development, and that the mechanism behind it is DPC proteolysis.