Transcriptional analysis of the conserved ftsZ gene cluster in Mycoplasma genitalium and Mycoplasma pneumoniae
Transcriptional analysis of the conserved ftsZ gene cluster in Mycoplasma genitalium and Mycoplasma pneumoniae
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DOI：
10.1128/jb.187.13.4542-4551.2005
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发表时间：
2005-07-01
影响因子：
3.2
通讯作者：
Hutchison, CA
中科院分区：
文献类型：
--
作者：
Benders, GA;Powell, BC;Hutchison, CA
采用几种实验方法构建了生殖支原体及其近亲肺炎支原体中系统发育保守的FtsZ细胞分裂基因簇的详细转录图谱。我们确定了该簇的起始点和终止点，以及每个基因的绝对稳定RNA水平。这一簇在这两种生物中的转录被证明是高度链特异性的。虽然这一簇中的四个基因是共转录的，但它们的转录单位也包括两个功能相近但功能不同的基因。在生殖支原体中发现了这两个基因上游的转录起始点，但在肺炎支原体中没有检测到。在肺炎支原体中，这六个基因的转录终止于一个多(U)尾发夹。在生殖支原体中，这种转录以一种未知的机制终止于两个相距较近的点。实时定量逆转录-聚合酶链式反应分析表明，在肺炎支原体的这个簇中，所有6个基因的mRNA水平最多相差5倍，并且在簇的开始处随着距离启动子的距离的增加而形成一个递减量的梯度。编码区的信使核糖核酸含量约为基因间区的20-100倍。我们估计我们检测到的最丰富的mRNA是每个细胞0.6个拷贝。我们得出结论，在生殖支原体和肺炎支原体中，一组功能相关的基因通常在启动子之前，但很少跟随在终止子之后。这导致在这些生物体中，功能无关的基因通常是共转录的。
Several experimental approaches were used to construct a detailed transcriptional profile of the phylogenetically conserved ftsZ cell division gene cluster in both Mycoplasma genitalium and its closest relative, Mycoplasma pneumoniae. We determined initiation and termination points for the cluster, as well as an absolute steady-state RNA level for each gene. Transcription of this cluster in both these organisms was shown to be highly strand specific. While the four genes in this cluster are cotranscribed, their transcription unit also includes two genes of close proximity yet disparate function. A transcription initiation point immediately upstream of these two genes was detected in M. genitalium but not M. pneumoniae. In M. pneumoniae, transcription of the six genes terminates at a poly(U)-tailed hairpin. In M. genitalium, this transcription terminates at two closely spaced points by an unknown mechanism. Real-time reverse transcription-PCR analysis of this cluster in M. pneumoniae shows that mRNA levels for all six genes vary at most fivefold and form a gradient of decreasing quantity with increasing distance from the promoter at the beginning of the cluster. mRNA from coding regions was approximately 20- to 100-fold more abundant than that from intergenic regions. We estimated the most abundant mRNA we detected at 0.6 copy per cell. We conclude that groups of functionally related genes in M. genitalium and M. pneumoniae are often preceded by promoters but rarely followed by terminators. This causes functionally unrelated genes to be commonly cotranscribed in these organisms.