Partial Reduction in BRCA1 Gene Dose Modulates DNA Replication Stress Level and Thereby Contributes to Sensitivity or Resistance

• Published in: International journal of molecular sciences Vol. 23; no. 21; p. 13363
• Main Authors: Classen, Sandra, Rahlf, Elena, Jungwirth, Johannes, Albers, Nina, Hebestreit, Luca Philipp, Zielinski, Alexandra, Poole, Lena, Groth, Marco, Koch, Philipp, Liehr, Thomas, Kankel, Stefanie, Cordes, Nils, Petersen, Cordula, Rothkamm, Kai, Pospiech, Helmut, Borgmann, Kerstin
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.11.2022; MDPI
• Subjects: BRCA1; BRCA1 protein; BRCA1 Protein - genetics; BRCA1 Protein - metabolism; Breast cancer; Breast Neoplasms - drug therapy; Breast Neoplasms - genetics; Cell cycle; Cell Line, Tumor; CHK1; CHK1 protein; Cloning; CRISPR; Deoxyribonucleic acid; DNA; DNA biosynthesis; DNA Damage; DNA damage response; DNA repair; DNA Repair - genetics; DNA Replication; Domains; Double-strand break repair; Female; Genes, BRCA1; Homologous Recombination; Humans; Ionizing radiation; irradiation; Medical prognosis; Mutation; Poly(ADP-ribose) polymerase; Protein expression; Proteins; Replication; replication stress; S phase; Sensitivity; replication stress; BRCA1; CHK1; homologous recombination; DNA damage response; irradiation
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms232113363

is a well-known breast cancer risk gene, involved in DNA damage repair via homologous recombination (HR) and replication fork protection. Therapy resistance was linked to loss and amplification of the gene causing inferior survival of breast cancer patients. Most studies have focused on the analysis of complete loss or mutations in functional domains of . How mutations in non-functional domains contribute to resistance mechanisms remains elusive and was the focus of this study. Therefore, clones of the breast cancer cell line MCF7 with indels in exon 9 and 14 were generated using CRISPR/Cas9. Clones with successful introduced mutations were evaluated regarding their capacity to perform HR, how they handle DNA replication stress (RS), and the consequences on the sensitivity to MMC, PARP1 inhibition, and ionizing radiation. Unexpectedly, mutations resulted in both increased sensitivity and resistance to exogenous DNA damage, despite a reduction of HR capacity in all clones. Resistance was associated with improved DNA double-strand break repair and reduction in replication stress (RS). Lower RS was accompanied by increased activation and interaction of proteins essential for the S phase-specific DNA damage response consisting of HR proteins, FANCD2, and CHK1.