Nutlin-3a suppresses poly (ADP-ribose) polymerase 1 by mechanisms different from conventional PARP1 suppressors in a human breast cancer cell line
Nutlin-3a suppresses poly (ADP-ribose) polymerase 1 by mechanisms different from conventional PARP1 suppressors in a human breast cancer cell line
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DOI：
10.18632/oncotarget.27581
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发表时间：
2020-05
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通讯作者：
Masaki Kobayashi;Yuka Ishizaki;M. Owaki;Y. Matsumoto;Yuri Kakiyama;Shunsuke Hoshino;Ryoma Tagawa;Yuka Sudo;Naoyuki Okita;K. Akimoto;Y. Higami
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作者：
Masaki Kobayashi;Yuka Ishizaki;M. Owaki;Y. Matsumoto;Yuri Kakiyama;Shunsuke Hoshino;Ryoma Tagawa;Yuka Sudo;Naoyuki Okita;K. Akimoto;Y. Higami
聚腺苷二磷酸核糖聚合酶1（Poly（ADP-ribose）polymerase 1，PARP 1）在单链DNA修复中起重要作用。PARP 1抑制剂可增强DNA损伤药物在同源重组缺陷型肿瘤（包括乳腺癌易感基因（BRCA 1）突变的肿瘤）中的作用。Nutlin-3a是一种顺式咪唑啉类似物，可抑制小鼠双微体2（MDM 2）的降解并稳定p53。我们先前报道nutlin-3a以p53依赖的方式诱导小鼠成纤维细胞中的PARP 1降解，这表明nutlin-3a可能是PARP 1抑制剂。在这里，我们研究了nutlin-3a对人乳腺癌细胞系MCF-7中PARP 1的影响。与我们先前的结果一致，nutlin-3a在MCF-7细胞中以剂量和时间依赖性方式降低PARP 1水平，但这种降低在p53敲低细胞中受到抑制。RITA是一种与p53本身结合的p53稳定剂，但未能降低PARP 1蛋白水平。此外，瞬时MDM 2敲低抑制nutlin-3a介导的PARP 1减少。MG 132蛋白酶体抑制剂，以及用叉头和环指结构域（CHFR）和环指蛋白146（RNF 146）敲低检查点，靶向PARP 1的E3泛素连接酶，抑制nutlin-3a诱导的PARP 1减少。短期nutlin-3a处理提高了PAR化PARP 1的水平，表明nutlin-3a促进PARP 1的PAR化，从而诱导其蛋白酶体降解。此外，nutlin-3a诱导的PARP 1降解增强了顺铂在BRCA 1敲低细胞中的DNA损伤作用。我们的研究表明，nutlin-3a是一种PARP 1抑制剂，通过与MDM 2结合并促进PARP 1的autoPAR化来诱导PARP 1蛋白酶体降解。对nutlin-3a诱导的PARP 1降解机制的进一步分析可能会导致开发适用于BRCA 1突变癌症的新型PARP 1抑制剂。
Poly (ADP-ribose) polymerase 1 (PARP1) plays important roles in single strand DNA repair. PARP1 inhibitors enhance the effects of DNA damaging drugs in homologous recombination-deficient tumors including tumors with breast cancer susceptibility gene (BRCA1) mutation. Nutlin-3a, an analog of cis-imidazoline, inhibits degradation of murine double minute 2 (MDM2) and stabilizes p53. We previously reported that nutlin-3a induces PARP1 degradation in p53-dependent manner in mouse fibroblasts, suggesting nutlin-3a may be a PARP1 suppressor. Here, we investigated the effects of nutlin-3a on PARP1 in MCF-7, a human breast cancer cell line. Consistent with our previous results, nutlin-3a reduced PARP1 levels in dose- and time-dependent manners in MCF-7 cells, but this reduction was suppressed in p53 knockdown cells. RITA, a p53 stabilizer that binds to p53 itself, failed to reduce PARP1 protein levels. Moreover, transient MDM2 knockdown repressed nutlin-3a-mediated PARP1 reduction. The MG132 proteasome inhibitor, and knockdown of checkpoint with forkhead and ring finger domains (CHFR) and ring finger protein 146 (RNF146), E3 ubiquitin ligases targeting PARP1, suppressed nutlin-3a-induced PARP1 reduction. Short-term nutlin-3a treatment elevated the levels of PARylated PARP1, suggesting nutlin-3a promoted PARylation of PARP1, thereby inducing its proteasomal degradation. Furthermore, nutlin-3a-induced PARP1 degradation enhanced DNA-damaging effects of cisplatin in BRCA1 knockdown cells. Our study revealed that nutlin-3a is a PARP1 suppressor that induces PARP1 proteasomal degradation by binding to MDM2 and promoting autoPARylation of PARP1. Further analysis of the mechanisms in nutlin-3a-induced PARP1 degradation may lead to the development of novel PARP1 suppressors applicable for cancers with BRCA1 mutation.