HEAT-SHOCK RESPONSE OF MURINE CHLAMYDIA-TRACHOMATIS
HEAT-SHOCK RESPONSE OF MURINE CHLAMYDIA-TRACHOMATIS
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DOI：
10.1128/jb.172.12.6959-6972.1990
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发表时间：
1990-12-01
影响因子：
3.2
通讯作者：
GANEM, D
中科院分区：
文献类型：
--
作者：
ENGEL, JN;POLLACK, J;GANEM, D
我们研究了沙眼衣原体小鼠肺炎株的热休克反应。衣原体热激反应的动力学与其他原核生物相似：诱导过程很快，发生在 5 至 10 分钟的时间内，并在转录水平上受到调节。热休克蛋白 DnaK 和 GroEL 的免疫印迹分析和异源抗血清免疫沉淀表明，热休克后这两种蛋白的合成速率增加，但绝对量没有增加。通过对热休克诱导 mRNA 的基因进行一般筛选，我们鉴定并克隆了其中两个。 DNA序列分析表明其中一个基因是dnaK的同源物。对 dnaK 基因上游区域的进一步序列分析表明，grpE 基因的衣原体同源物位于紧邻 dnaK 基因的位置。第二个基因座编码三个潜在的非重叠开放阅读框。其中一个开放阅读框与大肠杆菌的核糖体蛋白 S18 有 52% 同源性，因此可能编码衣原体同源物。有趣的是，目前尚不清楚这种核糖体蛋白是由大肠杆菌中的热休克诱导的。 S1 核酸酶和引物延伸分析将 dnaK 转录物的起始位点定位到 grpE 编码序列的最后一个核苷酸，表明这两个基因虽然串联排列，但却是分开转录的。在沙眼衣原体 dnaK、grpE 或 S18 基因上游均未鉴定出与大肠杆菌共有热休克启动子相似的启动子序列。热休克对 dnaK 和 S18 mRNA 的诱导发生在转录水平；它们的诱导可以被利福平阻断。然而，这两个基因座的诱导机制并不相同。他们对氯霉素的敏感性不同。 dnaK mRNA 的诱导需要蛋白质从头合成，而 S18 mRNA 的诱导则不需要。 因此，沙眼衣原体利用至少两种不同的途径来诱导编码热激反应中诱导的蛋白质的mRNA的转录。
We have investigated the heat shock response in the mouse pneumonitis strain of Chlamydia trachomatis. The kinetics of the chlamydial heat shock response resembled that of other procaryotes: the induction was rapid, occurring over a 5- to 10-min time period, and was regulated at the level of transcription. Immunoblot analysis and immunoprecipitations with heterologous antisera to the heat shock proteins DnaK and GroEL demonstrated that the rate of synthesis, but not the absolute amount of these two proteins, increased after heat shock. Using a general screen for genes whose mRNAs are induced by heat shock, we identified and cloned two of these. DNA sequence analysis demonstrated that one of the genes is a homolog of dnaK. Further sequence is analysis of the region upstream of the dnaK gene revealed that the chlamydial homolog of the grpE gene is located just adjacent to the dnaK gene. The second locus encoded three potential nonoverlapping open reading frames. One of the open reading frames was 52% homologous to the ribosomal protein S18 of Escherichia coli and thus presumably encodes the chlamydial homolog. Interestingly, this ribosomal protein is not known to be induced by heat shock in E. coli. S1 nuclease and primer extension analyses located the start site of the dnaK transcript to the last nucleotide of the grpE coding sequence, suggesting that these two genes, although tandemly arranged, are transcribed separately. No promoter sequences resembling the E. coli consensus heat shock promoter could be identified upstream of either the C. trachomatis dnaK, grpE, or S18 gene. The induction of the dnaK and S18 mRNAs by heat shock occurred at a transcriptional level; their induction could be blocked by rifampin. The mechanisms of induction for these two loci were not the same, however; they were differentially sensitive to chloramphenicol. Whereas the induction of dnaK mRNA required de novo protein synthesis, the induction of the S18 mRNA did not. Thus, C. trachomatis utilizes at least two different pathways to induce the transcription of mRNAs encoding proteins induced in the heat shock response.