Molecular mechanism of DNA-polymerase choice in vivo

描述（由申请人提供）：随着DNA聚合酶的新家族的最近发现，已经清楚的是，所有活生物体都具有比前导链和滞后链上的DNA的简单复制所需的多得多的DNA聚合酶。人类至少拥有16种DNA聚合酶，即使是简单的大肠杆菌也有5种。许多新发现的DNA聚合酶具有特殊的功能，使细胞能够在环境挑战中生存。跨损伤聚合酶允许复制体穿过特定的DNA损伤，否则会阻止正常的复制聚合酶，从而在损伤超过DNA修复能力时存活。在这样做时，一些跨损伤聚合酶引入突变，并且许多是对无损伤DNA高度致突变的低保真度聚合酶。因此，使用这些低保真度聚合酶似乎需要在环境损伤的立即存活和诱变之间进行权衡，这可能导致真核生物中的致癌作用，并可能降低微生物的适应性。因此，选择在复制体中使用哪种DNA聚合酶是一个关键的细胞决策。聚合酶选择的关键是复制滑动钳蛋白（真核生物中的PCNA和大肠杆菌中由DNAN编码的β）。coli）。该项目使用一种新的测定方法来确定β钳的哪些部分以及如何介导5E的竞争。大肠杆菌的DNA聚合酶，并在体内的DNA聚合酶的选择功能：一个关键的调节决定，细胞生存的环境损害，和基因组健康。

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.