Molecular Mechanisms of Radiation and Chemical Mutagenesis

为了阐明辐射诱变和化学诱变的分子机制，我们研究了大肠杆菌中已知参与诱变的基因产物的生化特性。本项目的主要成果如下：在dna受损细胞中活化的RecA蛋白促进UnuD和MucA蛋白的裂解，从而激活这些蛋白的诱变作用。我们证明了polB基因受LexA抑制因子（SOS调控）的负调控，并且由polB编码的DNA聚合酶II在结构和功能上与真核生物的复制性DNA聚合酶同源。我们已经证明RuvA四聚体与RuvB形成稳定的配合物，并且该配合物与同源重组中间体Holliday结构特异性相互作用，促进分支迁移。我们从生物化学的角度证明了RuvC蛋白是一种特殊的能分解Holliday连接的内切酶。

To elucidate molecular mechanisms of radiation and chemical mutagenesis, we have studiedbiochemical properties of the products of the genes which are known to be involved in mutagenesis in Escherichia coli. The major accomplishments of this project are as follows.1. RecA protein activated in the DNA-damaged cell promotes cleavage of UnuD and MucA proteins and thereby activates these proteins for mutagenesis.2. We demonstrated that the polB gene is negatively regulated by LexA repressor (SOS regulation) and that DNA polymerase II encoded by polB is structurally and functionally homologous to replicative DNA polymerases of eukaryotes.3. We have proved that a RuvA tetramer and RuvB form a stable complex and the complex interacts specifically with the Holliday structure, an intermediate of homologous recombination, and promotes branch migration.4. We demonstrated biochemically that RuvC protein is a specific endonuclease that resolves the Holliday junction.