School of Biomedical Sciences, LKS Faculty of Medicine, The University of Hong Kong, Hong Kong S.A.R.
Center for Synthetic Biology Engineering Research, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen 518055, PR China.
Nucleic Acids Res. 2018 Nov 2;46(19):10119-10131. doi: 10.1093/nar/gky775.
The RING finger protein TRAIP protects genome integrity and its mutation causes Seckel syndrome. TRAIP encodes a nucleolar protein that migrates to UV-induced DNA lesions via a direct interaction with the DNA replication clamp PCNA. Thus far, mechanistically how UV mobilizes TRAIP from the nucleoli remains unknown. We found that PCNA binding is dispensable for the nucleolus-nucleoplasm shuttling of TRAIP following cell exposure to UV irradiation, and that its redistribution did not rely on the master DNA damage kinases ATM and ATR. Interestingly, I-PpoI-induced ribosomal DNA damage led to TRAIP exclusion from the nucleoli, raising the possibility that active ribosomal DNA transcription may underlie TRAIP retention in the nuclear sub-compartments. Accordingly, chemical inhibition of RNA polymerase I activity led to TRAIP diffusion into the nucleoplasm, and was coupled with marked reduction of DNA/RNA hybrids in the nucleoli, suggesting that TRAIP may be sequestered via binding to nucleic acid structures in the nucleoli. Consistently, cell pre-treatment with DNase/RNase effectively released TRAIP from the nucleoli. Taken together, our study defines a bipartite mechanism that drives TRAIP trafficking in response to UV damage, and highlights the nucleolus as a stress sensor that contributes to orchestrating DNA damage responses.
RING 指蛋白 TRAIP 可保护基因组完整性，其突变可导致 Seckel 综合征。TRAIp 编码一种核仁蛋白，可通过与 DNA 复制夹子 PCNA 的直接相互作用迁移到 UV 诱导的 DNA 损伤处。迄今为止，尚不清楚 UV 如何将 TRAIP 从核仁中动员起来。我们发现，PCNA 结合对于 TRAIP 在细胞暴露于 UV 照射后从核仁到核质的穿梭是可有可无的，并且其重新分布不依赖于主 DNA 损伤激酶 ATM 和 ATR。有趣的是，I-PpoI 诱导的核糖体 DNA 损伤导致 TRAIP 从核仁中排除，这表明活跃的核糖体 DNA 转录可能是 TRAIP 在核亚区保留的基础。因此，RNA 聚合酶 I 活性的化学抑制导致 TRAIP 扩散到核质中，并伴有核仁中 DNA/RNA 杂交的显著减少，表明 TRAIP 可能通过与核仁中的核酸结构结合而被隔离。一致地，用 DNase/RNase 预处理细胞可有效地将 TRAIP 从核仁中释放出来。总之，我们的研究定义了一个双分机制，该机制可驱动 TRAIP 对 UV 损伤的易位，并强调核仁作为应激传感器，有助于协调 DNA 损伤反应。
