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Proc Natl Acad Sci U S A. 2015 Aug 18;112(33):E4565-70. doi: 10.1073/pnas.1505356112. Epub 2015 Aug 3.

Fork rotation and DNA precatenation are restricted during DNA replication to prevent chromosomal instability.

Author information

1
Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, United Kingdom;
2
Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, United Kingdom; School of Biochemistry, University of Bristol, Bristol BS8 1TD, United Kingdom.
3
Genome Damage and Stability Centre, University of Sussex, Falmer, Brighton, East Sussex BN1 9RQ, United Kingdom; jon.baxter@sussex.ac.uk.

Abstract

Faithful genome duplication and inheritance require the complete resolution of all intertwines within the parental DNA duplex. This is achieved by topoisomerase action ahead of the replication fork or by fork rotation and subsequent resolution of the DNA precatenation formed. Although fork rotation predominates at replication termination, in vitro studies have suggested that it also occurs frequently during elongation. However, the factors that influence fork rotation and how rotation and precatenation may influence other replication-associated processes are unknown. Here we analyze the causes and consequences of fork rotation in budding yeast. We find that fork rotation and precatenation preferentially occur in contexts that inhibit topoisomerase action ahead of the fork, including stable protein-DNA fragile sites and termination. However, generally, fork rotation and precatenation are actively inhibited by Timeless/Tof1 and Tipin/Csm3. In the absence of Tof1/Timeless, excessive fork rotation and precatenation cause extensive DNA damage following DNA replication. With Tof1, damage related to precatenation is focused on the fragile protein-DNA sites where fork rotation is induced. We conclude that although fork rotation and precatenation facilitate unwinding in hard-to-replicate contexts, they intrinsically disrupt normal chromosome duplication and are therefore restricted by Timeless/Tipin.

KEYWORDS:

DNA catenation; DNA replication; DNA topology; fork rotation; topoisomerases

PMID:
26240319
PMCID:
PMC4547287
DOI:
10.1073/pnas.1505356112
[Indexed for MEDLINE]
Free PMC Article

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