Molecular mechanism of DNA-polymerase choice in vivo

描述(由申请人提供)：随着最近新的DNA聚合酶家族的发现，很明显，所有活着的生物体都拥有比在领先和滞后链上简单复制DNA所需的DNA聚合酶多得多的DNA聚合酶。人类至少有16种DNA聚合酶，即使是简单的大肠杆菌也有5种已知的DNA聚合酶。许多新发现的DNA聚合酶具有特殊的功能，允许细胞在应对环境挑战时存活。跨病变聚合酶允许复制体穿越特定的DNA损伤，否则这些损伤会阻止正常的复制聚合酶，当病变超过DNA修复能力时，允许存活。在这样做的过程中，一些跨病变聚合酶会引入突变，许多是低保真的聚合酶，对无病变的DNA具有高度突变作用。因此，使用这些低保真聚合酶似乎需要在环境侮辱和突变之间进行权衡，这可能会导致真核生物的癌症发生，并可能降低微生物的适合性。因此，选择在复制体上使用哪种DNA聚合酶是一个关键的细胞决定。聚合酶选择中的一个关键因素是复制的滑动夹蛋白(真核生物中的增殖细胞核抗原和大肠杆菌中由DNAN编码的β蛋白)。本项目使用一种新的分析方法来确定β钳的哪些部分以及如何介导5种大肠杆菌DNA聚合酶的竞争，以及在体内DNA聚合酶选择中的功能：这是环境损害和基因组健康对细胞生存的关键调控决定。

DESCRIPTION (provided by applicant): With the recent discoveries of new families of DNA polymerases, it has become clear that all living organisms possess many more DNA polymerases than are needed for simple replication of DNA on leading and lagging strands. Humans possess at least 16 DNA polymerases and even the simple bacterium Escherichia colt has 5 currently known. Many of the newly-discovered DNA polymerases carry out specialized functions that allow cell survival in response to environmental challenges. The translesion polymerases allow the replisome to traverse specific DNA lesions that otherwise block normal replicative polymerases, allowing survival when lesions exceed DNA-repair capacity. In doing this, some translesion polymerases introduce mutations, and many are low-fidelity polymerases that are highly mutagenic on lesion-free DNA. Thus, use of these low-fidelity polymerases appears to entail a trade-off between immediate survival of environmental insults and mutagenesis, which can lead to carcinogenesis in eukaryotes, and potentially to reduced fitness in microbes. The choice of which DNA polymerase is used at the replisome is therefore a critical cellular decision. A key player in polymerase choice is the replicative sliding-clamp proteins (PCNA in eukaryotes and beta, encoded by DNAN, in E. coli). This project uses a novel assay for determining which parts of, and how, the beta clamp mediates competition of the 5 E. coli DNA polymerases, and functions in DNA polymerase choice in vivo: a critical regulatory decision for cell survival of environmental damage, and genomic health.