DNA Repair and Differentiation in B. subtilis

所有活着的细胞都会不断地暴露在能够改变DNA初级结构的化学和物理介质中。因此，应该预料到，所有生物体似乎都有移除或修复这种损害的机制。在过去的三十年里，人们一直致力于阐明存在的各种DNA修复机制，以及这些修复系统与细胞生存、突变、基因重组、DNA复制、癌症发生、毒理学、分化和发育的关系。革兰氏阳性芽胞形成菌枯草芽孢杆菌是研究DNA修复与分化相互作用的模型。具体地说，当枯草杆菌分化为其胜任状态时，这种SOS系统的某些方面被自发激活。本研究主要对DIN基因和recA基因的损伤诱导和活性特异性诱导的分子机制进行了研究。这些基因的操纵子/启动子区域已经被分离和测序。调控元件、转录起始点已初步确定。初步数据表明，参与其中一些基因的调控的复杂调控网络的存在，特别是recA启动子。利用分子生物学和遗传学技术，如S1核酸酶保护、凝胶迁移率改变分析、Western blotts、DNA测序、克隆突变分析、聚合酶链式反应、转座子失活等，将解决以下问题：1)哪些DNA序列对recA基因的损伤诱导表达是必需的；和2)哪些DNA序列对于recA基因的能力特异性诱导是必不可少的？%该奖项应该为细菌细胞如何调节他们对环境压力反应的一个重要方面。

All living cells are constantly exposed to chemical and physical agents that have the ability to alter the primary structure of DNA. Thus, it should be expected that all organisms appears to have mechanisms for the removal or repair of this damage. During the last thirty years, a great of effort has been placed on trying to elucidate the various DNA repair mechanisms that exist as well as the relationship of these repair systems to cell survival, mutagenesis, genetic recombination, DNA replication, carcinogenesis, toxicology, differentiation and development. The Gram positive spore-forming bacterium Bacillus subtilis a model for the study of the interactions of DNA repair with differentiation. Specifically, aspects of this SOS system are spontaneously activated when B. subtilis differentiates into its competent state. The present study concentrates on the molecular mechanisms that regulate the damage induction and the competence specific induction of din(DNA damage inducible) genes and of the recA gene. Operator/promoter regions from these genes have been isolated and sequenced. Regulatory elements, transcription start sites have been tentatively identified. The preliminary data suggest the existence of complex regulatory networks involved in the regulation of some of these genes, especially the recA promoter. Using the appropriate techniques of molecular biology and genetics, such as S1 nuclease protection, gel mobility shift assays, Western Blots, DNA sequencing, cloning mutational analysis, polymerase chain reaction, transposon inactivation, etc, the following questions will be addressed: 1) What DNA sequences are essential for the damage inducible expression of the recA gene; and 2) what DNA sequences are essential for the competence specific induction of the recA gene? %%% This award should provide detailed insight into how bacterial cells regulate an important aspect of their response to environmental stress.