Inhibition of DNA damage repair by artificial activation of PARP with siDNA

Abstract

One of the major early steps of repair is the recruitment of repair proteins at the damage site, and this is coordinated by a cascade of modifications controlled by phosphatidylinositol 3-kinase-related kinases and/or poly (ADP-ribose) polymerase (PARP). We used short interfering DNA molecules mimicking double-strand breaks (called Dbait) or single-strand breaks (called Pbait) to promote DNA-dependent protein kinase (DNA-PK) and PARP activation. Dbait bound and induced both PARP and DNA-PK activities, whereas Pbait acts only on PARP. Therefore, comparative study of the two molecules allows analysis of the respective roles of the two signaling pathways: both recruit proteins involved in single-strand break repair (PARP, XRCC1 and PCNA) and prevent their recruitment at chromosomal damage. Dbait, but not Pbait, also inhibits recruitment of proteins involved in double-strand break repair (53BP1, NBS1, RAD51 and DNA-PK). By these ways, Pbait and Dbait disorganize DNA repair, thereby sensitizing cells to various treatments. Single-strand breaks repair inhibition depends on direct trapping of the main proteins on both molecules. Double-strand breaks repair inhibition may be indirect, resulting from the phosphorylation of double-strand breaks repair proteins and chromatin targets by activated DNA-PK. The DNA repair inhibition by both molecules is confirmed by their synthetic lethality with BRCA mutations.

Drug-Driven Synthetic Lethality: Bypassing Tumor Cell Genetics with a Combination of AsiDNA and PARP Inhibitors

“…AsiDNA, a molecule of Dbait family, consists of a 32 base pair oligonucleotide forming a double helix that mimics a DSB. AsiDNA acts by hijacking and hyper-activating PARP1 (13) and the DNA-dependent protein kinase (DNA-PK) (14) which modify the chromatin and consequently inhibit the recruitment of many proteins involved in the HR and NHEJ pathways at the damage sites (14). This strategy sensitizes tumors to DNA damaging therapies such as radiotherapy and chemotherapy (15)(16)(17)(18).…”

The DNA Repair Inhibitor Dbait Is Specific for Malignant Hematologic Cells in Blood

“…Thus, repair enzymes do not aggregate at damage site and do not form foci after irradiation in Dbaittreated cells with a pan nuclear phosphorylation of H2AX induced by DNA-PK activation. Repair of single-strand and double-strand DNA breaks [via SSB repair (17), nonhomologous end joining (15), and homologous recombination (18)] is impaired in Dbaittreated cells. AsiDNA is the clinical form of Dbait.…”

The DNA Repair Inhibitor DT01 as a Novel Therapeutic Strategy for Chemosensitization of Colorectal Liver Metastasis

“…These molecules are short double-stranded DNA with a free double-strand blunt end, which target key damage signal transducers such as DNA-dependent protein kinase (DNA-PK; ref, 9) and PARP (10), triggering their activation and amplifying false damage signaling. Consequently, the recruitment of downstream DNA repair enzymes is impaired, inhibiting several DNA repair pathways such as homologous recombination (9), nonhomologous end joining (8,9), base excision repair, and singlestrand break repair (10) leading to an accumulation of unrepaired damage causing cell death.…”