Choosing how to restart stalled DNA replication forks

What is it about?

In this review, we examine how cells respond when DNA-copying machines, called replication forks, stall at DNA damage, tightly bound proteins, breaks, or other obstacles. We compare mechanisms in Escherichia coli and eukaryotic cells, especially yeast, that can restart replication while trying to preserve genetic information. A central theme is that cells do not have one simple response: they must choose between more accurate routes, such as repair, fork reversal, template switching, and homologous recombination, and more risky translesion synthesis, which copies past damage but can introduce mutations. We highlight how this choice is regulated by systems such as the E. coli SOS response, PCNA modification in Saccharomyces cerevisiae, and the eukaryotic DNA damage checkpoint.

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Why is it important?

Stalled replication forks are dangerous because the genome still has to be fully copied, but restarting replication in the wrong way can threaten genome stability. This review helps organize how different organisms balance completion of DNA replication with the need to avoid unnecessary mutation or harmful recombination. It also suggests why the regulation of replication restart may be relevant to understanding genome instability, including processes connected with cancer in higher organisms.

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