A small RNA inhibits translation of the histone-like protein Hc1 in Chlamydia trachomatis
A small RNA inhibits translation of the histone-like protein Hc1 in Chlamydia trachomatis
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DOI：
10.1111/j.1365-2958.2005.04949.x
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发表时间：
2006-01-01
影响因子：
3.6
通讯作者：
Hackstadt, T
中科院分区：
文献类型：
--
作者：
Grieshaber, NA;Grieshaber, SS;Hackstadt, T
衣原体基本体（EB）的染色质由与真核H1序列同源的蛋白质稳定。这些组蛋白同源物，称为HC 1和HC 2，只在衣原体生命周期的后期阶段表达，伴随着网状体（RB）重组成代谢不活跃的EB。HC 1和HC 2在类核结构的建立以及RB分化回EB时基因表达的下调中起主要作用。Hc1对基因表达模式的影响需要衣原体严格控制Hc1活性。因此，HC1的表达和活性受到转录和转录后的调节。我们在这里描述了一个小的调节RNA（sRNA），作为一个额外的检查点，负调控HC 1的合成。与hctA，编码HC1的基因，在大肠杆菌中的sRNA的共表达抑制HC1的翻译，但不影响hctA mRNA的转录或稳定性。IhtA（hctA翻译抑制剂）仅存在于纯化的RB中，而HC 1仅存在于纯化的EB中。在感染过程中，IhtA，但不是HC 1，存在于RB和下调，而HC 1上调RB EB分化。因此，我们建议，IhtA是一个全球性的监管电路，控制分化的RB到EB在衣原体的生命周期。
The chromatin of chlamydial elementary bodies (EBs) is stabilized by proteins with sequence homology to eukaryotic H1. These histone homologues, termed Hc1 and Hc2, are expressed only during the late stages of the chlamydial life cycle concomitant with the reorganization of reticulate bodies (RBs) into metabolically inactive EBs. Hc1 and Hc2 play a major role in establishment of nucleoid structure as well as in downregulation of gene expression as RBs differentiate back to EBs. The effects of Hc1 on gene expression patterns requires that chlamydiae strictly control Hc1 activity. Hc1 expression and activity are thus regulated transcriptionally as well as post-transcriptionally. We describe here a small regulatory RNA (sRNA) that acts as an additional checkpoint to negatively regulate Hc1 synthesis. Coexpression of the sRNA with hctA, the gene that encodes Hc1, in Escherichia coli inhibited Hc1 translation but did not affect hctA mRNA transcription or stability. IhtA (inhibitor of hctA translation) was present only in purified RBs while Hc1 was present only in purified EBs. During infection IhtA, but not Hc1, was present in RBs and was downregulated while Hc1 was upregulated upon RB to EB differentiation. Thus, we propose that IhtA is part of a global regulatory circuit that controls differentiation of RBs to EBs during the chlamydial life cycle.