Fig 2: DNA damage induces MORC2 K767Ac in a PARP1-dependent manner. A MCF-7 cells were pretreated with or without 10 µM ATM inhibitor (KU-55933), 10 µM ATR inhibitor (VE-821), 10 µM DNA-PKcs inhibitor (NU7441), and 10 µM PARP inhibitor (Olaparib) for 3 h, and then treated with 1 mM MMS for 1 h. IP and immunoblotting analyses were performed with the indicated antibodies. Positive controls for these inhibitors are shown in the input. B HEK293T cells stably expressing pCDH and Flag-MORC2 were pretreated with or without 10 µM Olaparib for 3 h, and then treated with 1 mM MMS for another 2 h or 6 Gy IR. IP and immunoblotting analyses were performed with the indicated antibodies. C MCF-7 and BT549 cells were pretreated with or without 10 µM Olaparib for 3 h, and then treated with 1 mM MMS for another 2 h or 6 Gy IR. IP and immunoblotting analyses were performed with the indicated antibodies. D WT and PARP1-KO MCF-7 cells were treated with or without 1 mM MMS for 2 h or 6 Gy IR. Thereafter, IP and immunoblotting analyses were carried out with the inidicated antibodies. E BT549 cells were transfected with siNC or two independent siRNA targeting PARP1 (siPARP1). After 48 h of transfection, cells were treated with or without 1 mM MMS for 2 h or 6 Gy IR. IP and immunoblotting analyses were subsequently performed with the indicated antibodies

Fig 3: PARylation of NAT10 by PARP1 regulates its nucleoplasmic translocation and co-localization with MORC2. A MCF-7 cells were transfected with plasmid DNAs encoding Flag-MORC2, HA-NAT10, or HA-NAT10 K3A. After 48 h of transfection, cells were treated with or without 1 mM MMS for 2 h or 6 Gy IR. IF staining was performed with an anti-Flag (green) or anti-HA (red) antibody. DNA was counterstained with DAPI (blue). Scale bar, 2.5 μm. The quantitative results of cells with NAT10 nucleoplasmic translocation are presented in the right panel. **p < 0.01; NS, no significance. B, C MCF-7 cells were transfected with HA-NAT10 and Flag-MORC2. After 48 h of transfection, cells were pretreated with or without 10 μM Olaparib for 3 h, and then treated with or without 1 mM MMS for another 2 h (B) or 6 Gy IR (C). IF staining was performed with an anti-Flag (green) or anti-HA (red) antibody. DNA was counterstained with DAPI (blue). Scale bar, 2.5 μm. The quantitative results of cells with NAT10 nucleoplasmic translocation are displayed in the right panel. **p < 0.01; ***p < 0.001. D, E PARP1-KO MCF-7 cells were transfected with HA-NAT10 and Flag-MORC2. After 48 h of transfection, cells were treated with or without 1 mM MMS for another 2 h (D) or 6 Gy IR (E). IF staining was performed with an anti-Flag (green) or anti-HA (red) antibody. DNA was counterstained with DAPI (blue). Scale bar, 2.5 μm. The quantitative results of cells with NAT10 nucleoplasmic translocation are displayed in the right panel. **p < 0.01; ***p < 0.001. Arrows indicate the colocalization between MORC2 and NAT10

Fig 4: PARylation of NAT10 by PARP1 regulates MORC2 acetylation in response to DNA damage. A, B NAT10-KO MCF-7 and BT549 cells were transfected with plasmid DNAs encoding pCDH, HA-NAT10, or HA-NAT10 K3A. After 48 h of transfection, cells were treated with or without 1 mM MMS for 2 h (A) or 6 Gy IR (B), and then subjected to IP and immunoblotting with the indicated antibodies

Fig 5: The proposed working model. Activated PARP1 after DNA damage catalyzes the PARylation of NAT10, which is required for the translocation of NAT10 from the nucleolus to the nucleoplasm. NAT10 relocalization increases its co-localization and interaction with its substrate, MORC2, thereby enhancing MORC2 K767Ac in response to DNA damage