Heterogeneous nuclear ribonucleoprotein L facilitates recruitment of 53BP1 and BRCA1 at the DNA break sites induced by oxaliplatin in colorectal cancer
Heterogeneous nuclear ribonucleoprotein L facilitates recruitment of 53BP1 and BRCA1 at the DNA break sites induced by oxaliplatin in colorectal cancer
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异质核核糖核蛋白 L 促进结直肠癌中奥沙利铂诱导的 DNA 断裂位点 53BP1 和 BRCA1 的募集
DOI：
10.1038/s41419-019-1784-x
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发表时间：
2019-07-18
影响因子：
9
通讯作者：
Zhou, Zongguang
中科院分区：
文献类型：
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作者：
Hu, Wenjun;Lei, Linping;Zhou, Zongguang
尽管奥沙利铂是治疗结直肠癌（CRC）的有效化疗药物，但肿瘤细胞可以形成逃避奥沙利铂诱导的细胞死亡的机制，并对这种药物表现出高度耐受性和获得性耐药性。异质核核糖核蛋白 L (hnRNP L) 已被证明在 B 淋巴细胞 IgH 类别转换重组 (CSR) 期间的 DNA 修复中发挥关键作用，但其在 CRC 和化疗耐药中的作用仍不清楚。我们的研究旨在揭示奥沙利铂治疗的 CRC 细胞中 hnRNP L 调节 DNA 双链断裂 (DSB) 的未鉴定机制。在本研究中，我们观察到 hnRNP L 的敲除增强了 DNA 断裂水平和 CRC 细胞对奥沙利铂的敏感性。关键 DNA 修复因子（BRCA1、53BP1 和 ATM）的表达不受 hnRNP L 敲低的影响，因此排除了 hnRNP L 通过 mRNA 调节介导的可能性。此外，我们观察到CRC细胞（SW620和HCT116）中ATM的磷酸化水平与53BP1和BRCA1相反变化，这通过奥沙利铂加hnRNP L损伤表现出协同作用。在这些关键修复因子的病灶形成中也观察到类似的现象。我们还发现 hnRNP L 通过其 RNA 识别基序 (RRM) 直接与这些 DNA 修复因子结合。细胞死亡分析表明，在奥沙利铂孵育下，hnRNP L 的 RRM 是细胞存活所必需的。总之，hnRNP L 对于奥沙利铂诱导的 DSB 中 DNA 修复因子的募集至关重要。靶向 hnRNP L 是一种很有前途的新临床方法，可以增强目前奥沙利铂耐药患者化疗的有效性。
Although oxaliplatin is an effective chemotherapeutic drug for treatment of colorectal cancer (CRC), tumor cells can develop mechanisms to evade oxaliplatin-induced cell death and show high tolerance and acquired resistance to this drug. Heterogeneous nuclear ribonucleoprotein L (hnRNP L) has been proved to play a critical role in DNA repair during IgH class switch recombination (CSR) in B lymphocytes, while, its role in CRC and chemotherapeutic resistance remain unknown. Our study aims to uncover an unidentified mechanism of regulating DNA double-strand breaks (DSBs) by hnRNP L in CRC cells treated by oxaliplatin. In present study, we observed that knockdown of hnRNP L enhanced the level of DNA breakage and sensitivity of CRC cells to oxaliplatin. The expression of key DNA repair factors (BRCA1, 53BP1, and ATM) was unaffected by hnRNP L knockdown, thereby excluding the likelihood of hnRNP L mediation via mRNA regulation. Moreover, we observed that phosphorylation level of ATM changed oppositely to 53BP1 and BRCA1 in the CRC cells (SW620 and HCT116) which exhibit synergistic effect by oxaliplatin plus hnRNP L impairment. And similar phenomenon was observed in the foci formation of these critical repair factors. We also found that hnRNP L binds directly with these DNA repair factors through its RNA-recognition motifs (RRMs). Analysis of cell death indicated that the RRMs of hnRNP L are required for cell survival under incubation with oxaliplatin. In conclusion, hnRNP L is critical for the recruitment of the DNA repair factors in oxaliplatin-induced DSBs. Targeting hnRNP L is a promising new clinical approach that could enhance the effectiveness of current chemotherapeutic treatment in patients with resistance to oxaliplatin.