tRNA基因启动子起动整合性接合元件ICEKp1整合酶转录的机制研究

肺炎克雷伯菌是我国临床分离最常见的革兰阴性病原菌之一，其毒力因子耶尔森菌素的合成基因簇位于整合性接合元件ICEKp1上。ICEKp1可携带毒力基因进行自主转移，但机制尚不清楚。ICEKp1整合酶特异地识别染色体tRNA-asn基因位点；在ICEKp1整合时，整合酶基因紧邻tRNA-asn基因3’-端，且两个基因转录方向一致。前期实验发现，整合酶基因和tRNA-asn基因可共转录；整合在不同tRNA-asn基因位点的ICEKp1转移频率有明显差异。我们由此假设，ICEKp1整合状态下tRNA-asn基因启动子可起动整合酶基因的转录，启动子活性可能影响ICEKp1的转移。本项目将：(1)确定ICEKp1整合状态下整合酶基因的启动子，(2)分析tRNA-整合酶基因多顺反子转录本的剪切，(3)比较tRNA-asn基因启动子活性对ICEKp1转移的影响，以期为遏制毒力基因转移提供新的思路。

Klebsiella pneumoniae is one of the most common pathogens of nosocomial infection. Biosynthetic gene clusters for yersiniabactin and other important virulence factors are frequently located within the integrative and conjugative element, ICEKp1; however, its transfer mechanism is unknown. The ICEKp1-encoding integrase recognizes the 3'-end of the tRNA-asn gene, and is involved in the key process of ICE self-transfer, including chromosomal excision and integration. In different K. pneumoniae strains, ICEKp1 is inserted into the different tRNA-asn gene sites; we previously observed that the transcription level of ICEKp1 integrase genes was significantly different, which might be related to the activity of the upstream tRNA-asn gene promoter. In this study, we aim to : (1) characterize the promoter region of ICEKp1 integrase gene, (2) analyze the cutting process of the tRNA-int polycistronic transcript, and (3) explore the effect of tRNA-asn gene promoter on ICEKp1 transfer. This research may be helpful for the inhibition of the horizontal transfer of bacterial virulence genes.