HdiR-like蛋白调控猪链球菌耐药相关ICEs水平传播的分子机制

整合接合元件（ICEs）是介导细菌耐药基因水平传播的重要载体，在猪链球菌中广泛存在。研究显示部分细菌可通过LexA或HdiR依赖的SOS应答系统调控ICEs转移，但猪链球菌缺少该应答系统，其ICEs转移调控机制尚属未知。申请者前期研究显示ICESa2603家族ICEs可表达类似HdiR的蛋白（HdiR-like），并证实其在DNA损伤导致ICEs剪切环化过程中呈高表达，推测其参与ICEs的转移调控。本项目拟采用基因敲除、定点突变、EMSA、Chip-Seq等技术，进一步通过鉴定激活ICEs转移的各类DNA损伤压力、验证HdiR-like的DNA结合和自我切割功能，重点阐明缺少HdiR依赖的SOS应答系统的猪链球菌如何通过HdiR-like感受DNA损伤进而调控ICEs水平转移这个科学问题。该项目的完成对控制猪链球菌耐药性水平传播具有深远意义，并为开发抗基因水平转移药物的研究提供理论基础。

Integrative conjugative elements (ICEs) are major vectors for horizontal transfer of antibiotic resistance genes which is widespread in bacteria including Streptococcus suis. Previous reports show that LexA- or HdiR-dependent SOS responses can activate the transfer of ICEs in some bacterium species. But little is known about how Streptococcus suis which lacks LexA-like repressor (HdiR) trigger the horizontal transfer of ICEs. Now we identified a HdiR-like protein in ICESa2603 family ICEs which had a high expression level responsed to DNA damage. Based on our preliminary data we generated the hypothesis that HdiR-like protein involves in the transfer of ICEs. To approve the hypothesis we will (1) evaluate the sensitivity of HdiR-like to a variety of exogenous and endogenous stresses; (2) analyze DNA binding and self-cleavage function of HdiR-like using recombinant protein; and (3) study the ways of HdiR-like regulated the horizontal transfer of ICEs in response to DNA damage. The study will answer the question whether and how ICEs transfer in response to DNA damage, and to provide a theoretical basis for the development of drugs targeting horizontal gene transfer.