RECQ5-dependent SUMO2 conjugation of PCNA in the resolution of transcription-replication conflicts

项目摘要 增殖细胞核抗原（PCNA）是复制体的重要组成部分，它增强了细胞的增殖。 DNA聚合酶在DNA合成中的持续合成能力。此外，作为对DNA损伤的反应，PCNA 在赖氨酸164（K164）处泛素化以绕过DNA损伤。在未受干扰的细胞中，相同的K164残基可以 也与SUMO 1或SUMO 2结合，SUMO 1-PCNA与PARI的募集有关 解旋酶以抑制同源重组。然而，引发复制障碍的根源 PCNA SUMO化尚未被定义，并且PCNA SUMO化的调节因子也不清楚。也不 明确SUMO 2-PCNA是否与SUMO 1-PCNA功能冗余。我们最新公布的数据表明， SUMO 2-PCNA在转录中具有SUMO 1-PCNA所不具有的独特功能，因为只有 SUMO 2-PCNA与转录活性染色质相关。尽管PCNA SUMO 2结合 发生在S期，SUMO 2-PCNA由RNA聚合酶II依赖性转录诱导，需要 RNA聚合酶II相互作用蛋白，RECQ 5 DNA解旋酶。重要的是，SUMO 2-PCNA降低的细胞 在S期积累转录诱导的DNA双链断裂。因此，我们的数据支持 SUMO 2-PCNA在解决转录-复制冲突中的作用的概念性创新模型， 最小化基因组不稳定性。该建议的目标是（1）确定促进细胞增殖的分子因子， 转录诱导的SUMO 2结合PCNA，（2）以确定SUMO 2- PCNA解决了转录-复制冲突，（3）阐明SUMO 2-PCNA对 防止基因组不稳定性和肿瘤转化，因为转录-复制冲突是主要的 常见脆性部位不稳定性的来源。

Project Summary Proliferating cell nuclear antigen (PCNA) is an essential component of the replisome, and it enhances the processivity of the DNA polymerases in DNA synthesis. In addition, in response to DNA damage, PCNA is ubiquitinated at lysine 164 (K164) to bypass DNA lesions. In unperturbed cells, the same K164 residue can also be conjugated with either SUMO1 or SUMO2, and SUMO1-PCNA has been implicated in recruiting PARI helicase to suppress homologous recombination. However, the source of replication obstacle that triggers PCNA SUMOylation is yet to be defined, and the regulators of PCNA SUMOylation are not known. It is also not clear if SUMO2-PCNA functions redundantly to SUMO1-PCNA. Our newly published data argue that human SUMO2-PCNA has a unique function in transcription that is not shared by SUMO1-PCNA, because only SUMO2-PCNA is associated with transcriptionally active chromatin. Even though PCNA SUMO2 conjugation occurs in S-phase, SUMO2-PCNA is induced by RNA polymerase II - dependent transcription and requires the RNA polymerase II - interacting protein, RECQ5 DNA helicase. Importantly, cells with reduced SUMO2-PCNA accumulate transcription-induced DNA double-strand breaks during S-phase. Therefore, our data support a conceptually innovative model for a role of SUMO2-PCNA in resolving transcription-replication conflicts to minimize genomic instability. The goal of this proposal is (1) to identify the molecular factors that facilitate the transcription-induced SUMO2 conjugation of PCNA, (2) to identify the molecular mechanism by which SUMO2- PCNA resolves transcription-replication conflicts, and (3) to elucidate the contribution of SUMO2-PCNA toward preventing genomic instability and neoplastic transformation, as transcription-replication conflicts are major source for common fragile site instability.