POLθ processes ssDNA gaps and promotes replication fork progression in BRCA1-deficient cells

POLθ processes ssDNA gaps and promotes replication fork progression in BRCA1-deficient cells

Polymerase theta (POLθ) is an error-prone DNA polymerase whose loss is synthetically lethal in cancer cells bearing breast cancer susceptibility proteins 1 and 2 (BRCA1/2) mutations. To investigate the basis of this genetic interaction, we utilized a small-molecule inhibitor targeting the POLθ polym...

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Published in:Cell reports (Cambridge) Vol. 41; no. 9; p. 111716
Main Authors: Schrempf, Anna, Bernardo, Sara, Arasa Verge, Emili A., Ramirez Otero, Miguel A., Wilson, Jordan, Kirchhofer, Dominik, Timelthaler, Gerald, Ambros, Anna M., Kaya, Atilla, Wieder, Marcus, Ecker, Gerhard F., Winter, Georg E., Costanzo, Vincenzo, Loizou, Joanna I.
Format: Journal Article
Language:English
Published: United States Elsevier Inc 29-11-2022
Subjects:
BRCA1
Cell Division
Cell Nucleus
DNA, Single-Stranded - genetics
Mutation
Nucleotidyltransferases
POLθ
replication stress
ssDNA
synthetic lethality
CP: Molecular biology
replication stress
BRCA1
POLθ
ssDNA
synthetic lethality
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Summary:Polymerase theta (POLθ) is an error-prone DNA polymerase whose loss is synthetically lethal in cancer cells bearing breast cancer susceptibility proteins 1 and 2 (BRCA1/2) mutations. To investigate the basis of this genetic interaction, we utilized a small-molecule inhibitor targeting the POLθ polymerase domain. We found that POLθ processes single-stranded DNA (ssDNA) gaps that emerge in the absence of BRCA1, thus promoting unperturbed replication fork progression and survival of BRCA1 mutant cells. A genome-scale CRISPR-Cas9 knockout screen uncovered suppressors of the functional interaction between POLθ and BRCA1, including NBN, a component of the MRN complex, and cell-cycle regulators such as CDK6. While the MRN complex nucleolytically processes ssDNA gaps, CDK6 promotes cell-cycle progression, thereby exacerbating replication stress, a feature of BRCA1-deficient cells that lack POLθ activity. Thus, ssDNA gap formation, modulated by cell-cycle regulators and MRN complex activity, underlies the synthetic lethality between POLθ and BRCA1, an important insight for clinical trials with POLθ inhibitors. [Display omitted] •POLθ suppresses the formation of single-stranded DNA gaps•POLθ suppresses replication stress, which is exacerbated upon BRCA1 deficiency•The gap-filling activity of POLθ becomes limiting in BRCA1-deficient cells Schrempf and Bernardo et al. show that POLθ, known for its role in DNA double-strand break repair, is involved in filling single-stranded DNA gaps. This function becomes limiting in BRCA1-deficient cells, providing new insights into the genetic interaction between BRCA1 and POLθ that is currently exploited in clinical trials.
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ISSN:2211-1247
2211-1247
DOI:10.1016/j.celrep.2022.111716