Pathway of Spontaneous Mutagenesis in Escherichia coli

描述（由申请方提供）：本研究的长期目标是更好地了解细胞中发生的自发诱变机制。与突变的产生直接相关的是细胞用来将突变事件保持在低水平发生的保真度机制。受突变事件影响的人类疾病和病症的列表是广泛的，并且范围从所谓的单基因遗传病症到通过环境因素和发生以实现改变的表型的多个突变事件的组合效应而产生的多因素病症。即使是曾经被认为几乎完全是环境性的传染病，现在也知道会受到宿主和病原体基因型的影响。体细胞突变导致多种人类癌症。虽然人们对环境化学诱变剂引起的突变事件给予了极大的关注，但很可能发生在人群中的大多数突变事件本质上是自发的。 研究自发突变机制的一个直接方法是表征突变等位基因，称为抗突变等位基因，其导致自发突变频率降低。这是可能的遗传特征良好的细菌，大肠杆菌。将对一系列疑似或部分表征的抗突变体等位基因进行全面检测和表征，目的是揭示致突变途径。由于这种途径和保持突变事件在低频率的保真度机制是非常保守的，预计从这项细菌研究中获得的结果将适用于其他生物体，包括人类。 在过去的几年里，许多研究共同表明，自发突变发生在饥饿或压力细菌细胞。其中一些突变是由一组专门的DNA聚合酶的作用引起的，这些聚合酶能够合成过去受损或不寻常的DNA模板。在大肠已经表明，这些聚合酶中的一种或多种在饥饿/应激细胞中可能是有活性的，其中显然通过受损模板的合成以产生突变为“代价”。本申请旨在更全面地表征在这些生理条件下突变的产生。人类拥有许多这些专门的DNA聚合酶，其活性可能是人类突变负荷的重要部分。

DESCRIPTION (provided by applicant): The long-term objective of this study is to acquire a greater understanding of the mechanisms of spontaneous mutagenesis as they occur in cells. Directly related to the creation of mutations is the fidelity mechanisms that cells employ to keep mutational events at a low level of occurrence. The list of human diseases and disorders that are affected by mutational events is extensive and ranges from the so-called single gene genetic disorders to multifactorial conditions that come about via the combined effects of environmental factors and multiple mutational events that occur to achieve the altered phenotype. Even infectious diseases once thought to be almost exclusively environmental in nature are now known to be influenced by the genotype of both the host and the pathogen. Somatic mutations give rise to the variety of human cancers. While great attention has been given to mutational events caused by environmental chemical mutagens, it is likely that most mutational events that occur in human populations are spontaneous in nature. A direct approach to study mechanisms of spontaneous mutagenesis is to characterize mutant alleles, called antimutator alleles that cause decreases in spontaneous mutation frequencies. This is possible with the genetically well-characterized bacterium, Escherichia coli. A series of suspected or partially characterized antimutator alleles will be fully tested and characterized with the goal of revealing mutagenic pathways. Since such pathways and the fidelity mechanisms that keep mutational events at a low frequency are well conserved, it is expected that results obtained from this bacterial study would be applicable to other organisms, including humans. For the past several years, many studies have collectively shown that spontaneous mutations occur in starving or stressed bacterial cells. Some of these mutations are caused by the action of a group of specialized DNA polymerases that are capable of synthesizing past damaged or unusual DNA templates. In E. coli it has been shown that one or more of these polymerases may be active in starving/stressed cells where apparently the synthesis past a damaged template comes at a "cost" of creating mutations. The present application intends to more fully characterize the creation of mutations under these physiological conditions. Humans possess a number of these specialized DNA polymerases whose activities may be responsible for a significant portion of the human mutational load.