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bioRxiv · 10.1101/2022.12.18.520715

An auto-release mechanism for HMCES-DNA-protein crosslinks

Donsbach, M.·Dürauer, S.·Nguyen, K. T.·Grünert, F.·Yaneva, D.·Semlow, D.·Stingele, J.
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Abstract

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 and cleavage by APE1 endonuclease. In contrast, HMCES-DPCs are quickly 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.

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Donsbach, M., Dürauer, S., Nguyen, K. T., Grünert, F., Yaneva, D., Semlow, D., Stingele, J.. 2022-12-19. An auto-release mechanism for HMCES-DNA-protein crosslinks. https://doi.org/10.1101/2022.12.18.520715

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