Regulation of the Mycobacterium tuberculosishypoxic response gene encoding alpha-crystallin. Mycobacterium tuberculosis

Unlike many pathogens that are overtly toxic to their hosts, the primary virulence determinant of Mycobacterium tuberculosis appears to be its ability to persist for years or decades within humans in a clinically latent state. Since early in the 20th century latency has been linked to hypoxic conditions within the host, but the response of M. tuberculosis to a hypoxic signal remains poorly characterized. The M. tuberculosis alpha-crystallin (acr) gene is powerfully and rapidly induced at reduced oxygen tensions, providing us with a means to identify regulators of the hypoxic response. Using a whole genome microarray, we identified >100 genes whose expression is rapidly altered by defined hypoxic conditions. Numerous genes involved in biosynthesis and aerobic metabolism are repressed, whereas a high proportion of the induced genes have no known function. Among the induced genes is an apparent operon that includes the putative two-component response regulator pair Rv3133cy Rv3132c. When we interrupted expression of this operon by targeted disruption of the upstream gene Rv3134c, the hypoxic regulation of acr was eliminated. These results suggest a possible role for Rv3132cy3133cy3134c in mycobacterial latency. Keywords: comparative genome hybridization design and stimulus or stress design Overall design: Six samples were analyzed. The quality controls were biological replicate and technical replicate

与多数对宿主具有显性毒性的病原体不同，结核分枝杆菌（Mycobacterium tuberculosis）的主要毒力决定因子似乎是其能够在人体中以临床潜伏状态存活数年乃至数十年的能力。早在20世纪初期，学界便将结核分枝杆菌的潜伏感染与宿主体内的低氧环境相关联，但该菌对低氧信号的应答机制仍未被充分阐明。结核分枝杆菌的α-晶体蛋白（alpha-crystallin，缩写acr）基因在氧分压降低时会被强力且快速地诱导表达，这为我们鉴定低氧应答调控因子提供了可行途径。本研究借助全基因组微阵列（whole genome microarray）技术，鉴定出100余个基因，其表达会在特定低氧条件下发生快速改变：众多参与生物合成与有氧代谢的基因被抑制，而大部分诱导表达的基因功能尚不明确。在诱导表达的基因中，存在一个疑似操纵子（operon），其包含推定的双组分应答调控因子（two-component response regulator）对Rv3133c与Rv3132c。当我们通过靶向破坏上游基因Rv3134c来阻断该操纵子的表达时，acr基因的低氧调控效应被完全消除。上述结果表明，Rv3132c、Rv3133c与Rv3134c可能在分枝杆菌潜伏感染中发挥潜在作用。
关键词：比较基因组杂交设计与刺激/应激设计
整体实验设计：共分析6份样本，质量控制采用生物学重复与技术重复方案。