Experimentally revised repertoire of putative contingency loci in Neisseria meningitidis strain MC58:: evidence for a novel mechanism of phase variation
Experimentally revised repertoire of putative contingency loci in Neisseria meningitidis strain MC58:: evidence for a novel mechanism of phase variation
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DOI：
10.1046/j.1365-2958.2003.03678.x
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发表时间：
2003-10-01
影响因子：
3.6
通讯作者：
Moxon, ER
中科院分区：
文献类型：
--
作者：
Martin, P;van de Ven, T;Moxon, ER
对脑膜炎奈瑟菌MC58株的基因组序列分析发现了65个与简单序列重复相关的基因。在这65个假定的相变基因中，只有14个存在相变的实验证据。我们研究了其余51个基因的相变电势。与这51个基因中的20个相关的重复序列在26个不同的遗传菌株中被测序。这一分析根据重复基序的序列和长度，为候选基因的相变性提供了支持或反对的间接证据。使用菌落免疫印迹或β-半乳糖苷酶作为报告，对这些候选基因中的三个证实了这些阶段变异性的预测。这项研究发现了一个新的与重复序列(Taaa)相关的新的阶段变量基因(NMB1994或NADA)，以前没有报道与脑膜炎奈瑟氏菌的阶段变量基因相关。对NADA转录本的分析表明，该重复区域位于NADA启动子-35元件的上游。半定量逆转录聚合酶链式反应表明，重复次数的变化与NADA表达水平的变化有关，这一发现与可变重复次数(TaaA)调节启动子强度的模型一致。
Analysis of the genome sequence of Neisseria meningitidis strain MC58 revealed 65 genes associated with simple sequence repeats. Experimental evidence of phase variation exists for only 14 of these 65 putatively phase variable genes. We investigated the phase variable potential of the remaining 51 genes. The repeat tract associated with 20 of these 51 genes was sequenced in 26 genetically distinct strains. This analysis provided circumstantial evidence for or against the phase variability of the candidate genes, based on the sequence and the length of the repeated motif. These predictions of phase variability were substantiated for three of these candidate genes using colony immunoblotting or beta-galactosidase as a reporter. This investigation identified a novel phase variable gene (NMB1994 or nadA) associated with a repeat tract (TAAA) not previously reported to be associated with phase variable genes in N. meningitidis. Analysis of the nadA transcript revealed that the repeat tract was located upstream of the putative - 35 element of the nadA promoter. Semiquantitative RTPCR showed that variation in the number of repeats was associated with changes in the level of expression of nadA, findings consistent with a model whereby the variable number of ( TAAA) repeats modulates the promoter strength.