Boulares A H, Yakovlev A G, Ivanova V, Stoica B A, Wang G, Iyer S, Smulson M
Department of Biochemistry and Molecular Biology, Georgetown University School of Medicine, Washington, D.C. 20007, USA.
J Biol Chem. 1999 Aug 13;274(33):22932-40. doi: 10.1074/jbc.274.33.22932.
An early transient burst of poly(ADP-ribosyl)ation of nuclear proteins was recently shown to be required for apoptosis to proceed in various cell lines (Simbulan-Rosenthal, C., Rosenthal, D., Iyer, S., Boulares, H., and Smulson, M. (1998) J. Biol. Chem. 273, 13703-13712) followed by cleavage of poly(ADP-ribose) polymerase (PARP), catalyzed by caspase-3. This inactivation of PARP has been proposed to prevent depletion of NAD (a PARP substrate) and ATP, which are thought to be required for later events in apoptosis. The role of PARP cleavage in apoptosis has now been investigated in human osteosarcoma cells and PARP -/- fibroblasts stably transfected with a vector encoding a caspase-3-resistant PARP mutant. Expression of this mutant PARP increased the rate of staurosporine and tumor necrosis factor-alpha-induced apoptosis, at least in part by reducing the time interval required for the onset of caspase-3 activation and internucleosomal DNA fragmentation, as well as the generation of 50-kilobase pair DNA breaks, thought to be associated with early chromatin unfolding. Overexpression of wild-type PARP in osteosarcoma cells also accelerated the apoptotic process, although not to the same extent as that apparent in cells expressing the mutant PARP. These effects of the mutant and wild-type enzymes might be due to the early and transient poly(ADP-ribose) synthesis in response to DNA breaks, and the accompanying depletion of NAD apparent in the transfected cells. The accelerated NAD depletion did not seem to interfere with the later stages of apoptosis. These results indicate that PARP activation and subsequent cleavage have active and complex roles in apoptosis.
最近研究表明，核蛋白的早期短暂多聚（ADP - 核糖基）化是多种细胞系发生凋亡所必需的（辛布兰 - 罗森塔尔，C.，罗森塔尔，D.，艾耶尔，S.，布莱拉斯，H.，和斯穆尔森，M.（1998年）《生物化学杂志》273卷，13703 - 13712页），随后多聚（ADP - 核糖）聚合酶（PARP）被半胱天冬酶 - 3催化裂解。有人提出，PARP的这种失活可防止NAD（一种PARP底物）和ATP耗竭，而NAD和ATP被认为是凋亡后期事件所必需的。现在已经在人骨肉瘤细胞和稳定转染了编码抗半胱天冬酶 - 3的PARP突变体载体的PARP - / - 成纤维细胞中研究了PARP裂解在凋亡中的作用。这种突变体PARP的表达增加了星形孢菌素和肿瘤坏死因子 - α诱导的凋亡速率，至少部分是通过缩短半胱天冬酶 - 3激活和核小体间DNA片段化开始所需的时间间隔，以及减少50千碱基对DNA断裂的产生，而这种DNA断裂被认为与早期染色质解折叠有关。野生型PARP在骨肉瘤细胞中的过表达也加速了凋亡过程，尽管程度不如表达突变体PARP的细胞明显。突变型和野生型酶的这些作用可能是由于响应DNA断裂而早期短暂的多聚（ADP - 核糖）合成，以及转染细胞中明显伴随的NAD耗竭。加速的NAD耗竭似乎并未干扰凋亡的后期阶段。这些结果表明，PARP激活及随后的裂解在凋亡中具有积极且复杂的作用。
