Translesion合成(TLS)是真核细胞利用的DNA损伤耐受性机制,可在阻碍高保真复制机制的病变中复制DNA。在TLS中,使用一系列专门的DNA聚合酶,识别特定的DNA损伤,插入核苷酸穿过损伤,并扩展扭曲的引物模板。这允许细胞以突变为代价来保持遗传完整性。在人类中,TLS酶包括Y家族,插入聚合酶,Poln,Poli,波尔κ,Rev1和B家族扩展聚合酶Polζ,而在酿酒酵母中只有Poln,存在Rev1和Polz。为了绕过DNA损伤,TLS聚合酶合作,组装成一个复杂的真核滑动夹具,PCNA,称为TLS突变组。突变体组装取决于TLS酶的模块化结构域和亚基之间的蛋白质-蛋白质相互作用(PPI),以及它们与PCNA和DNA的相互作用。虽然TLS聚合酶和PPIs各自模块绕过DNA损伤的结构机制是众所周知的,他们在TLS复合体的背景下合作的机制仍然难以捉摸。这篇综述着重于TLS聚合酶的结构研究,并描述了从最近的高分辨率Cryo-EM研究中出现的TLS全酶组装体的作用情况。
Translesion synthesis (TLS) is a mechanism of DNA damage tolerance utilized by eukaryotic cells to replicate DNA across lesions that impede the high-fidelity replication machinery. In TLS, a series of specialized DNA polymerases are employed, which recognize specific DNA lesions, insert nucleotides across the damage, and extend the distorted primer-template. This allows cells to preserve genetic integrity at the cost of mutations. In humans, TLS enzymes include the Y-family, inserter polymerases, Polη, Polι, Polκ, Rev1, and the B-family extender polymerase Polζ, while in S. cerevisiae only Polη, Rev1, and Polζ are present. To bypass DNA lesions, TLS polymerases cooperate, assembling into a complex on the eukaryotic sliding clamp, PCNA, termed the TLS mutasome. The mutasome assembly is contingent on protein-protein interactions (PPIs) between the modular domains and subunits of TLS enzymes, and their interactions with PCNA and DNA. While the structural mechanisms of DNA lesion bypass by the TLS polymerases and PPIs of their individual modules are well understood, the mechanisms by which they cooperate in the context of TLS complexes have remained elusive. This review focuses on structural studies of TLS polymerases and describes the case of TLS holoenzyme assemblies in action emerging from recent high-resolution Cryo-EM studies.