XAB2 depletion induces intron retention in POLR2A to impair global transcription and promote cellular senescence
XAB2 depletion induces intron retention in POLR2A to impair global transcription and promote cellular senescence
复制标题
XAB2 缺失会诱导 POLR2A 中的内含子保留，从而损害整体转录并促进细胞衰老
DOI：
10.1093/nar/gkz532
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发表时间：
2019-09-05
影响因子：
14.9
通讯作者：
Lei, Haixin
中科院分区：
文献类型：
--
作者：
Hou, Shuai;Qu, Dajun;Lei, Haixin
摘要XAB2是一种多功能蛋白质，参与转录、剪接、DNA修复和mRNA输出等过程。在这里，我们报告了POLR2A，RNA聚合酶II最大的催化亚基，作为XAB2耗尽后下调的主要靶基因。XAB2缺失导致POLR2A严重的剪接缺陷，内含子保留显著。这些缺陷导致POLR2A在RNA和蛋白质水平上的大量丢失，从而进一步损害了全球转录。剪接抑制剂Madrasin处理后，POLR2A的表达也有类似的降低。使用基于TMT的定量蛋白质组学筛选确定了几个与mRNA监测有关的蛋白质，包括表达上调的Dom34。抑制Dom34的翻译或缺失可通过稳定POLR2AmRNA的表达来挽救其表达。免疫沉淀进一步证实，XAB2与剪接体成分有关，对POLR2A的表达具有重要意义。结构域作图表明，XAB2的TPR基序2-4和11通过与SNW1相互作用而对POLR2A的表达起关键作用。最后，我们发现POLR2A介导了XAB2缺乏引起的细胞衰老。缺失XAB2或POLR2A通过上调P53和p21的表达来诱导细胞衰老，缺失XAB2或POLR2A后POLR2A重新表达可缓解细胞衰老。这些数据支持XAB2作为POLR2A表达的守护者，确保基因表达的全局性，从而拮抗细胞衰老。
Abstract XAB2 is a multi-functional protein participating processes including transcription, splicing, DNA repair and mRNA export. Here, we report POLR2A, the largest catalytic subunit of RNA polymerase II, as a major target gene down-regulated after XAB2 depletion. XAB2 depletion led to severe splicing defects of POLR2A with significant intron retention. Such defects resulted in substantial loss of POLR2A at RNA and protein levels, which further impaired global transcription. Treatment of splicing inhibitor madrasin induced similar reduction of POLR2A. Screen using TMT-based quantitative proteomics identified several proteins involved in mRNA surveillance including Dom34 with elevated expression. Inhibition of translation or depletion of Dom34 rescued the expression of POLR2A by stabilizing its mRNA. Immuno-precipitation further confirmed that XAB2 associated with spliceosome components important to POLR2A expression. Domain mapping revealed that TPR motifs 2–4 and 11 of XAB2 were critical for POLR2A expression by interacting with SNW1. Finally, we showed POLR2A mediated cell senescence caused by XAB2 deficiency. Depletion of XAB2 or POLR2A induced cell senescence by up-regulation of p53 and p21, re-expression of POLR2A after XAB2 depletion alleviated cellular senescence. These data together support that XAB2 serves as a guardian of POLR2A expression to ensure global gene expression and antagonize cell senescence.