Transcription-Replication Conflict Orientation Modulates R-Loop Levels and Activates Distinct DNA Damage Responses

Conflicts between transcription and replication are a potent source of DNA damage. Co-transcriptional R-loops could aggravate such conflicts by creating an additional barrier to replication fork progression. Here, we use a defined episomal system to investigate how conflict orientation and R-loop fo...

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Bibliographic Details
Published in:Cell 2017-08, Vol.170 (4), p.774-786.e19
Main Authors: Hamperl, Stephan, Bocek, Michael J., Saldivar, Joshua C., Swigut, Tomek, Cimprich, Karlene A.
Format: Article
Language:English
Subjects:
DNA Damage
DNA Replication
DNA Replication Timing
DNA-damage response
genome instability
Genomic Instability
HEK293 Cells
Humans
Plasmids
R-loops
replication stress
Transcription, Genetic
transcription-replication conflicts
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Summary:Conflicts between transcription and replication are a potent source of DNA damage. Co-transcriptional R-loops could aggravate such conflicts by creating an additional barrier to replication fork progression. Here, we use a defined episomal system to investigate how conflict orientation and R-loop formation influence genome stability in human cells. R-loops, but not normal transcription complexes, induce DNA breaks and orientation-specific DNA damage responses during conflicts with replication forks. Unexpectedly, the replisome acts as an orientation-dependent regulator of R-loop levels, reducing R-loops in the co-directional (CD) orientation but promoting their formation in the head-on (HO) orientation. Replication stress and deregulated origin firing increase the number of HO collisions leading to genome-destabilizing R-loops. Our findings connect DNA replication to R-loop homeostasis and suggest a mechanistic basis for genome instability resulting from deregulated DNA replication, observed in cancer and other disease states. [Display omitted] •R-loop dependent TRCs provoke distinct forms of genome instability and DNA damage•Head-on oriented TRCs promote R-loop formation and ATR activation•Co-directionally oriented TRCs resolve R-loops yet promote ATM activation•Replication stress and deregulated origin firing induce head-on TRCs and R-loops Collisions between transcription and replication complexes activate distinct DNA damage responses depending on whether they meet head-on or are moving in the same direction.
ISSN:0092-8674
1097-4172
DOI:10.1016/j.cell.2017.07.043