The Trim33 ubiquitin ligase limits E2f4-dependent DNA replication [RNA-seq]. The Trim33 ubiquitin ligase limits E2f4-dependent DNA replication [RNA-seq]

Deregulation of RNA polymerase II (RNAPII) by oncoproteins, such as transcription factor Myc, interferes with DNA replication and is a major source of DNA damage and genomic instability. Ubiquitination is a key pathway controlling RNAPII activity via modification of RNAPII subunits or associated regulatory proteins. We uncover a mechanism for genome maintenance by ubiquitin ligase Trim33 and transcription factor E2f4. We show that Trim33 promotes E2f4 protein turnover, restricting interactions of E2f4 with chromatin and with the Recql DNA helicase. Replicative stress blunts Trim33-dependent regulation, which stimulates Recql recruitment to chromatin and facilitates recovery of DNA synthesis. Deletion of Trim33 triggers chronic recruitment of Recql and accelerates DNA replication under stress, accompanied by compromised DDR signaling and DNA repair. Depletion of Trim33 in Myc-overexpressing cells leads to accumulation of replication-associated DNA damage and delays Myc-driven tumorigenesis. We propose that the Trim33-E2f4-Recql axis provides a mechanism to control DNA replication at transcriptionally active chromatin to maintain genome integrity. Overall design: Gene expression profiling of Trim33-WT and Trim33KO cells was perfromed using RNA-seq

癌蛋白（如转录因子Myc）介导的RNA聚合酶II（RNA polymerase II，RNAPII）失调，会干扰DNA复制过程，是引发DNA损伤与基因组不稳定性的主要诱因。泛素化是通过修饰RNAPII亚基或其相关调控蛋白以调控其活性的关键通路。本研究揭示了泛素连接酶Trim33与转录因子E2f4参与基因组维持的分子机制。研究发现，Trim33可促进E2f4的蛋白质周转，限制E2f4与染色质及Recql DNA解旋酶（Recql DNA helicase）的相互作用。复制应激会削弱Trim33依赖的调控通路，该过程可促进Recql向染色质的募集，并助力DNA合成的恢复。Trim33缺失会触发Recql的持续性募集，在应激条件下加速DNA复制，同时伴随DNA损伤应答（DDR）信号通路受损与DNA修复缺陷。在过表达Myc的细胞中敲除Trim33，会导致复制相关DNA损伤的积累，并延缓Myc驱动的肿瘤发生进程。本研究提出，Trim33-E2f4-Recql轴可通过调控转录活跃染色质区域的DNA复制，从而维持基因组完整性。总体实验设计：采用RNA测序（RNA-seq）对Trim33野生型（Trim33-WT）与Trim33敲除（Trim33KO）细胞进行基因表达谱分析。