Peddi Srinivasa R, Chattopadhyay Ranajoy, Naidu C V, Izumi Tadahide
Stanley S. Scott Cancer Center and Department of Otolaryngology, 533 Bolivar St. 5th Floor, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
Toxicology. 2006 Jul 5;224(1-2):44-55. doi: 10.1016/j.tox.2006.04.025. Epub 2006 Apr 27.
DNA single-strand breaks (SSB) activate poly (ADP-ribose) polymerase 1 (PARP1), which then polymerizes ADP-ribosyl groups on various nuclear proteins, consuming cellular energy. Although PARP1 has a role in repairing SSB, activation of PARP1 also causes necrosis and inflammation due to depletion of cellular energy. Here we show that the major mammalian apurinic/apyrimidinic (AP) endonuclease-1 (APE1), an essential DNA repair protein, binds to SSB and suppresses the activation of PARP1. APE1's high affinity for SSB requires Arg177, which is unique in mammalian APEs. PARP1's binding to the cleaved DNA was inhibited, and PARP1 activation was suppressed by the wild-type APE1, but not by the R177A mutant APE1 protein. Cells transiently transfected with the wild-type APE1 decreased the PARP1 activation after H2O2 treatment, while such suppression did not occur with the expression of the R177A APE1 mutant. These results suggest that APE1 suppresses the activation of PARP1 during the repair process of the DNA damage generated by oxidative stress, which may have an important implication for cells to avoid necrosis due to energy depletion.
DNA单链断裂（SSB）会激活聚（ADP - 核糖）聚合酶1（PARP1），PARP1随后会在各种核蛋白上聚合ADP - 核糖基，消耗细胞能量。虽然PARP1在修复SSB中发挥作用，但PARP1的激活也会因细胞能量耗竭而导致坏死和炎症。在此我们表明，主要的哺乳动物脱嘌呤/脱嘧啶（AP）核酸内切酶1（APE1），一种重要的DNA修复蛋白，会与SSB结合并抑制PARP1的激活。APE1对SSB的高亲和力需要Arg177，这在哺乳动物APE中是独特的。野生型APE1抑制了PARP1与切割后DNA的结合以及PARP1的激活，但R177A突变型APE1蛋白则没有。用野生型APE1瞬时转染的细胞在H2O2处理后降低了PARP1的激活，而R177A APE1突变体的表达则未出现这种抑制作用。这些结果表明，APE1在氧化应激产生的DNA损伤修复过程中抑制PARP1的激活，这可能对细胞避免因能量耗竭而坏死具有重要意义。
