Comparative proteome analysis of Brucella abortus 2308 and its virB type IV secretion system mutant reveals new T4SS-related candidate proteins

Brucella abortus is an alpha-2 proteobacteria with a type IV secretion system (T4SS) known as virB, which is necessary to gain virulence by building up a replicative vacuole associated with the endoplasmic reticulum of the host cell. A virB T4SS mutant of the B. abortus 2308 strain and its wild-type strain were grown in acid medium in order to obtain and analyze their proteomes, looking for putative proteins that may serve as T4SS substrates and those that may be subjected to T4SS regulation. A total of 47 overexpressed and 22 underexpressed proteins from the virB T4SS mutant strain were selected and sequenced. Some of the 69 analyzed proteins have not been described before either as over or under-expressed in relation to a virB T4SS mutation, whereas some of them have been already described by other groups as potentially important secretory proteins in other Brucella species. An important number of the proteins identified are outer membrane and periplasmic space protein, which makes them become particularly important new T4SS-related candidate proteins.     

非编码小RNA BSR0602在布鲁菌环境适应能力中的调控作用

BSR0602是位于布鲁菌染色体上的非编码小RNA,在前期研究中我们发现,BSR0602与布鲁菌的胞内生存能力相关.为了进一步研究BSR0602对布鲁菌胞内环境适应能力的调控作用,采用双向电泳技术对布鲁菌野生株16M和BSR0602过表达株的全菌蛋白质谱进行比较分析.结果显示,BSR0602过表达后,布鲁菌转运代谢蛋白和压力适应蛋白的表达发生变化. qRT-PCR和HIS表位标记实验结果进一步证实,BSR0602在转录和翻译水平均影响氧压力适应蛋白SodA的表达.相关表型实验结果显示,BSR0602过表达株对氧压力更为敏感,证实了BSR0602在布鲁菌适应氧压力中的作用.结果表明,非编码小RNA BSR0602作为布鲁菌的转录后调控因子,可通过调控压力适应蛋白的表达来影响布鲁菌的压力适应能力和胞内生存.     

Coincident Hfq binding and RNase E cleavage sites on mRNA and small regulatory RNAs

The Escherichia coli RNA chaperone Hfq was discovered originally as an accessory factor of the phage Qbeta replicase. More recent work suggested a role of Hfq in cellular physiology through its interaction with ompA mRNA and small RNAs (sRNAs), some of which are involved in translational regulation. Despite their stability under certain conditions, E. coli sRNAs contain putative RNase E recognition sites, that is, A/U-rich sequences and adjacent stem-loop structures. We show herein that an RNase E cleavage site coincides with the Hfq-binding site in the 5'-untranslated region of E. coli ompA mRNA as well as with that in the sRNA, DsrA. Likewise, Hfq protects RyhB RNA from in vitro cleavage by RNase E. These in vitro data are supported by the increased abundance of DsrA and RyhB sRNAs in an RNase E mutant strain as well as by their decreased stability in a hfq(-) strain. It is commonly believed that the RNA chaperone Hfq facilitates or promotes the interaction between sRNAs and their mRNA targets. This study reveals another role for Hfq, that is, protection of sRNAs from endonucleolytic attack.