Poly(ADP-ribose)polymerases are involved in microhomology mediated back-up non-homologous end joining in Arabidopsis thaliana

Abstract

Besides the KU-dependent classical non-homologous end-joining (C-NHEJ) pathway, an alternative NHEJ pathway first identified in mammalian systems, which is often called the back-up NHEJ (B-NHEJ) pathway, was also found in plants. In mammalian systems PARP was found to be one of the essential components in B-NHEJ. Here we investigated whether PARP1 and PARP2 were also involved in B-NHEJ in Arabidopsis. To this end Arabidopsis parp1, parp2 and parp1parp2 (p1p2) mutants were isolated and functionally characterized. The p1p2 double mutant was crossed with the C-NHEJ ku80 mutant resulting in the parp1parp2ku80 (p1p2k80) triple mutant. As expected, because of their role in single strand break repair (SSBR) and base excision repair (BER), the p1p2 and p1p2k80 mutants were shown to be sensitive to treatment with the DNA damaging agent MMS. End-joining assays in cell-free leaf protein extracts of the different mutants using linear DNA substrates with different ends reflecting a variety of double strand breaks were performed. The results showed that compatible 5'-overhangs were accurately joined in all mutants, that KU80 protected the ends preventing the formation of large deletions and that PARP proteins were involved in microhomology mediated end joining (MMEJ), one of the characteristics of B-NHEJ.

Aluminum-Dependent Terminal Differentiation of the Arabidopsis Root Tip Is Mediated through an ATR-, ALT2-, and SOG1-Regulated Transcriptional Response

“…As shown in Figure 7A, two independent brca1 loss-of-function mutants were modestly sensitive to a range of Al concentrations compared with Col-0 wild type, suggesting that BRCA1 plays a role in repair of Al-dependent DNA damage rather than transition of the root tip to endoreduplication. PARP2, in conjunction with PARP1, is a key component of microhomology-mediated end joining, which is one type of nonhomologous end joining (NHEJ) DNA repair mechanism that is related to base excision and single strand break repair (Jia et al, 2013). As shown in Figure 7B, loss of these two key components of microhomology-mediated end joining results in increased sensitivity to Al, consistent with Al acting as a DNA damage agent.…”

“…As shown in Figure 7B, loss of these two key components of microhomology-mediated end joining results in increased sensitivity to Al, consistent with Al acting as a DNA damage agent. Al hypersensitivity was even more pronounced for a parp1 parp2 ku80 triple loss-of-function mutant, which represents a severe reduction in capability to carry out both classical NHEJ (KU80-related) and alternative NHEJ (PARP1-and PARP2-related) (Jia et al, 2013). These results suggest that Al has substantive negative effects on DNA integrity that in part requires ATR and SOG1-dependent induction of BRCA1 and PARP2 to repair the damage.…”

“…Loss-of-function mutations for both BRCA1 (Block-Schmidt et al, 2011) and PARP2 (Jia et al, 2013), which are Al-inducible SOG1 targets, were tested for their capability to grow in the presence of AlCl 3 in a soaked gel environment (pH 4.2). As shown in Figure 7A, two independent brca1 loss-of-function mutants were modestly sensitive to a range of Al concentrations compared with Col-0 wild type, suggesting that BRCA1 plays a role in repair of Al-dependent DNA damage rather than transition of the root tip to endoreduplication.…”

A Defect in DNA Ligase4 Enhances the Frequency of TALEN-Mediated Targeted Mutagenesis in Rice

“…Many proteins involved in the altNHEJ pathway, such as poly (ADP-ribose) polymerase1 (PARP1), meiotic recombination 11 (MRE11)-radiation sensitive 50 (Rad50)-Nijmegen Breakage Syndrome 1 (NBS1), histone H, DNA Ligase III, and XRCC1, have been identified in mammalian cells (Audebert et al, 2004;Rosidi et al, 2008;Cheng et al, 2011). Recent studies have shown that Arabidopsis XRCC1, XPF, Lig1, and PARP1/PARP2 also function in the altNHEJ pathway (Waterworth et al, 2009;Charbonnel et al, 2010Charbonnel et al, , 2011Jia et al, 2013).…”

Effectiveness and Safety of Poly (ADP-ribose) Polymerase Inhibitors in Cancer Therapy: A Systematic Review and Meta-analysis

“…DSBs are repaired mainly through non-homologous end-joining (NHEJ) and homologous recombination repair (HRR) pathways, which two play complementary roles [7]. PARP1-dependent end-joining (PARP-EJ) is a backup NHEJ repair pathway; when NHEJ is defective, PARP1-EJ pathway is activated [8,9]. PARP inhibitors (such as Olaparib, Iniparib, Veliparib, Rucaparib, and Niraparib), a class of small-molecule drugs inhibiting PARP enzymes, can induce synthetic lethality in HRR deficiency cancer cells [10].…”