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EMBO J. 2018 Nov 26. pii: e99793. doi: 10.15252/embj.201899793. [Epub ahead of print]

R-loop formation during S phase is restricted by PrimPol-mediated repriming.

Author information

1
MRC Laboratory of Molecular Biology, Cambridge, UK.
2
Sir William Dunn School of Pathology, Oxford, UK.
3
Genome Damage & Stability Centre, School of Life Sciences, University of Sussex, Brighton, UK.
4
MRC Laboratory of Molecular Biology, Cambridge, UK jes@mrc-lmb.cam.ac.uk.

Abstract

During DNA replication, conflicts with ongoing transcription are frequent and require careful management to avoid genetic instability. R-loops, three-stranded nucleic acid structures comprising a DNA:RNA hybrid and displaced single-stranded DNA, are important drivers of damage arising from such conflicts. How R-loops stall replication and the mechanisms that restrain their formation during S phase are incompletely understood. Here, we show in vivo how R-loop formation drives a short purine-rich repeat, (GAA)10, to become a replication impediment that engages the repriming activity of the primase-polymerase PrimPol. Further, the absence of PrimPol leads to significantly increased R-loop formation around this repeat during S phase. We extend this observation by showing that PrimPol suppresses R-loop formation in genes harbouring secondary structure-forming sequences, exemplified by G quadruplex and H-DNA motifs, across the genome in both avian and human cells. Thus, R-loops promote the creation of replication blocks at susceptible structure-forming sequences, while PrimPol-dependent repriming limits the extent of unscheduled R-loop formation at these sequences, mitigating their impact on replication.

KEYWORDS:

DNA secondary structures; PrimPol; R‐loops; replication; repriming

PMID:
30478192
DOI:
10.15252/embj.201899793
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