Krause Darren R, Jonnalagadda Jyoti C, Gatei Magtouf H, Sillje Herman H W, Zhou Bin-Bing, Nigg Erich A, Khanna Kumkum
Signal Transduction Lab, Cancer and Cell Biology Division, Queensland Institute of Medical Research, 300 Herston Rd, Qld 4029, Australia.
Oncogene. 2003 Sep 4;22(38):5927-37. doi: 10.1038/sj.onc.1206691.
The human Tousled-like kinases 1 and 2 (TLK) have been shown to be active during S phase of the cell cycle. TLK activity is rapidly suppressed by DNA damage and by inhibitors of replication. Here we report that the signal transduction pathway, which leads to transient suppression of TLK activity after the induction of double-strand breaks (DSBs) in the DNA, is dependent on the presence of a functional ataxia-telangiectasia-mutated kinase (ATM). Interestingly, we have discovered that rapid suppression of TLK activity after low doses of ultraviolet (UV) irradiation or aphidicolin-induced replication block is also ATM-dependent. The nature of the signal that triggers ATM-dependent downregulation of TLK activity after UVC and replication block remains unknown, but it is not due exclusively to DSBs in the DNA. We also demonstrate that TLK suppression is dependent on the presence of a functional Nijmegan Breakage Syndrome protein (NBS1). ATM-dependent phosphorylation of NBS1 is required for the suppression of TLK activity, indicating a role for NBS1 as an adaptor or scaffold in the ATM/TLK pathway. ATM does not phosphorylate TLK directly to regulate its activity, but Chk1 does phosphorylate TLK1 GST-fusion proteins in vitro. Using Chk1 siRNAs, we show that Chk1 is essential for the suppression of TLK activity after replication block, but that ATR, Chk2 and BRCA1 are dispensable for TLK suppression. Overall, we propose that ATM activation is not linked solely to DSBs and that ATM participates in initiating signaling pathways in response to replication block and UV-induced DNA damage.
人类类Tousled激酶1和2（TLK）已被证明在细胞周期的S期具有活性。DNA损伤和复制抑制剂可迅速抑制TLK活性。在此我们报告，在DNA中诱导双链断裂（DSB）后导致TLK活性短暂抑制的信号转导途径，依赖于功能性共济失调毛细血管扩张突变激酶（ATM）的存在。有趣的是，我们发现低剂量紫外线（UV）照射或阿非迪霉素诱导的复制阻滞后TLK活性的快速抑制也是ATM依赖性的。在UVC和复制阻滞之后触发ATM依赖性下调TLK活性的信号性质尚不清楚，但它并非完全由DNA中的DSB引起。我们还证明，TLK的抑制依赖于功能性尼曼-匹克氏病断裂综合征蛋白（NBS1）的存在。NBS1的ATM依赖性磷酸化是抑制TLK活性所必需的，这表明NBS1在ATM/TLK途径中作为衔接子或支架发挥作用。ATM不会直接磷酸化TLK来调节其活性，但Chk1在体外确实会磷酸化TLK1 GST融合蛋白。使用Chk1小干扰RNA，我们表明Chk1对于复制阻滞后TLK活性的抑制至关重要，但ATR、Chk2和BRCA1对于TLK的抑制是可有可无的。总体而言，我们提出ATM的激活并非仅与DSB相关联，并且ATM参与启动响应复制阻滞和紫外线诱导的DNA损伤的信号通路。
