DNA Repair and Differentiation in B. subtilis

所有活细胞都不断地暴露在能够改变DNA初级结构的化学和物理因素中。因此，我们应该预料到，所有生物体似乎都有清除或修复这种损伤的机制。在过去的三十年里，人们已经付出了巨大的努力，试图阐明存在的各种DNA修复机制，以及这些修复系统与细胞存活、突变、基因重组、DNA复制、致癌、毒理学、分化和发育的关系。革兰氏阳性芽孢形成细菌枯草芽孢杆菌是研究DNA修复与分化相互作用的模型。具体来说，当枯草芽孢杆菌分化到其主管状态时，这个SOS系统的各个方面就会自发激活。本文主要研究了DNA损伤诱导基因（din）和recA基因的损伤诱导和能力特异性诱导的分子机制。这些基因的操作子/启动子区域已被分离并测序。调控元件、转录起始位点已初步确定。初步数据表明，存在复杂的调控网络参与其中一些基因的调控，特别是recA启动子。利用分子生物学和遗传学的相关技术，如S1核酸酶保护、凝胶迁移位移测定、Western Blots、DNA测序、克隆突变分析、聚合酶链反应、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至关重要；2)哪些DNA序列对于recA基因的能力特异性诱导是必需的？该奖项将提供对细菌细胞如何调节其对环境应激反应的一个重要方面的详细见解。

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.