A non-proteolytic release mechanism for HMCES-DNA-protein crosslinks
Maximilian Donsbach, Sophie Dürauer, Florian Grünert, Kha T Nguyen, Richa Nigam, Denitsa Yaneva, Pedro Weickert, Rachel Bezalel-Buch, Daniel R Semlow and Julian Stingele. A non-proteolytic release mechanism for HMCES-DNA-protein crosslinks. The EMBO Journal (2023)e113360. https://doi.org/10.15252/embj.2022113360
Abstract cited directly from the article:
The conserved protein HMCES crosslinks to abasic (AP) sites in ssDNA to prevent strand scission and the formation of toxic dsDNA breaks during replication. Here, we report a non-proteolytic release mechanism for HMCES-DNA-protein crosslinks (DPCs), which is regulated by DNA context. In ssDNA and at ssDNA-dsDNA junctions, HMCES-DPCs are stable, which efficiently protects AP sites against spontaneous incisions or cleavage by APE1 endonuclease. In contrast, HMCES-DPCs are released in dsDNA, allowing APE1 to initiate downstream repair. Mechanistically, we show that release is governed by two components. First, a conserved glutamate residue, within HMCES' active site, catalyses reversal of the crosslink. Second, affinity to the underlying DNA structure determines whether HMCES re-crosslinks or dissociates. Our study reveals that the protective role of HMCES-DPCs involves their controlled release upon bypass by replication forks, which restricts DPC formation to a necessary minimum.