Kim Seung-Whan, Bae Yong-Goo, Pyo Suhk-Neung, Rhee Dong-Kwon
College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea.
Mol Cells. 2007 Apr 30;23(2):239-45.
DnaK is a major antigen in Streptococcus pneumoniae, and is induced by a minor shift in temperature (30 to 37 degrees ) but not by ethanol shock. Although HrcA in the presence of Ca++ represses the expression of both groEL and hrcA, the control of transcription of the dnaK operon is not completely understood. In this study, the dnaK operon of S. pneumoniae (5' hrcA-grpE-dnaK-dnaJ) was cloned and analyzed. It contains large intergenic regions in grpE/dnaK and dnaK/dnaJ. Pulse labeling with [35S]-methionine and immunoblot analyses revealed the presence of higher levels of DnaK than of HrcA even in the presence of Ca++ after heat shock suggesting that Ca++ differentially regulates the heat shock responses of hrcA and dnaK. By blocking de novo mRNA synthesis with rifampin it was shown that neither the hrcA nor the groEL transcripts were stabilized by heat shock even though dnaK transcripts were stabilized. We conclude that S. pneumoniae uses fine regulation of the transcription of the individual genes of the tetracistronic dnaK operon to cope with the various stresses experienced during infections.
DnaK是肺炎链球菌中的一种主要抗原，可由温度的微小变化（30至37摄氏度）诱导产生，但乙醇休克不能诱导其产生。尽管在有Ca++存在时HrcA会抑制groEL和hrcA的表达，但dnaK操纵子的转录调控机制尚未完全明确。在本研究中，对肺炎链球菌的dnaK操纵子（5' hrcA-grpE-dnaK-dnaJ）进行了克隆和分析。它在grpE/dnaK和dnaK/dnaJ中包含较大的基因间隔区。用[35S]-甲硫氨酸进行脉冲标记和免疫印迹分析表明，即使在热休克后有Ca++存在的情况下，DnaK的水平也高于HrcA，这表明Ca++对hrcA和dnaK的热休克反应有不同的调节作用。通过用利福平阻断从头mRNA合成发现，即使dnaK转录本被稳定，热休克也不会使hrcA或groEL转录本稳定。我们得出结论，肺炎链球菌通过对四顺反子dnaK操纵子中各个基因转录的精细调控来应对感染过程中所经历的各种应激。
