malS-5'UTR调节伤寒沙门菌耐酸力和侵袭力的作用机制研究

Prokaryotic non-coding RNAs (ncRNA) play an important role in response to environmental change and pathogenic processes. A new ncRNA, antisense RNA of bax (Asb), is discovered in human pathogen Salmonella enterica serovar Typhi (S. Typhi) by deep sequencing analysis of transcriptome. We verified the expression of Abs and identified Asb to be actually the 5' untranslated region (5' UTR) of malS gene in S. Typhi. We therefore renamed it as malS-5'UTR. We further found that deletion of malS-5'UTR increased the acid resistance and invasion ability on HeLa cells. Overexpression of malS-5'UTR decreases the mRNA and protein expression levels of bax. Other target genes of malS-5'UTR were found by using biology software. This project will determine the expressional characteristics of malS-5'UTR; Expression of acid stress and invasion related genes will be analyzed by genome microarray screening analysis and high-throughput RNA sequencing; Effect of malS-5'UTR on bax or other target genes will be studied to explain the related molecular mechanism. The project will reveal the expressional characteristics, mechanism of action of malS-5'UTR in acid resistance and invasion, and the importance in understanding the role of ncRNA played in regulation of environmental stress and pathogenesis of typhoid fever.

原核生物非编码RNA在细菌应对环境变化和致病过程中起重要作用。我们在伤寒沙门菌中通过转录组测序发现了一个非编码RNA，为bax的反义RNA，验证了其表达存在并确定其分子特征为malS基因的5’非翻译区，命名为malS-5'UTR；干预malS-5'UTR而不影响malS表达可以增加细菌的耐酸和侵袭力；malS-5'UTR的表达可以增加bax mRNA和蛋白表达水平；通过软件筛选出malS-5'UTR可能作用的其它靶基因。本项目将检测malS-5'UTR表达调节特性；通过基因组芯片和高通量RNA测序分别分析与酸应激和侵袭相关基因的表达；进一步研究malS-5'UTR与bax及其它靶基因的作用来阐述其作用的分子机制。本项目将揭示malS-5'UTR的表达调节特性、调节伤寒沙门菌耐酸和侵袭的作用机制，对于深刻理解非编码RNA在伤寒沙门菌应对环境应激及致病过程中的调节作用有重要意义。

非编码RNA作为重要的调节因子，在细菌适应并响应外界环境或宿主微环境的变化中起着重要作用。本项目对于伤寒沙门菌中新发现的非编码RNA——malS-5’UTR进行研究，发现malS-5’UTR在细菌迟滞期表达最高；在酸、氧、高渗应激条件下表达下调；sigma因子σE或者σS可能单独或一起参与了malS-5'UTR在应激条件下的转录调节。进一步发现malS-5'UTR通过与hisG mRNA碱基配对，阻碍HisG蛋白的生成，使得hisG的mRNA水平反馈性增加，而HisG蛋白的减少，使得细菌的耐酸力减弱，表现为高表达malS-5'UTR使得细菌在酸培养条件下生长速度明显减慢。最后，发现malS-5'UTR部分是通过抑制对侧靶基因bax的表达及增加细菌的动力来影响细菌侵袭力。本项目的研究对于深刻理解malS-5'UTR在伤寒沙门菌对环境压力的应答及其致病机制中的作用有着重要的意义。