School of Biomedical Sciences, University of Nottingham, Queen's Medical Centre, Nottingham, United Kingdom.
PLoS Genet. 2011 Jan 20;7(1):e1001277. doi: 10.1371/journal.pgen.1001277.
Neisseria meningitidis is the primary causative agent of bacterial meningitis. The genome is rich in repetitive DNA and almost 2% is occupied by a diminutive transposon called the Correia element. Here we report a bioinformatic analysis defining eight subtypes of the element with four distinct types of ends. Transcriptional analysis, using PCR and a lacZ reporter system, revealed that two ends in particular encode strong promoters. The activity of the strongest promoter is dictated by a recurrent polymorphism (Y128) at the right end of the element. We highlight examples of elements that appear to drive transcription of adjacent genes and others that may express small non-coding RNAs. Pair-wise comparisons between three meningococcal genomes revealed that no more than two-thirds of Correia elements maintain their subtype at any particular locus. This is due to recombinational class switching between elements in a single strain. Upon switching subtype, a new allele is available to spread through the population by natural transformation. This process may represent a hitherto unrecognized mechanism for phase variation in the meningococcus. We conclude that the strain-to-strain variability of the Correia elements, and the large number of strong promoters encoded by them, allows for potentially widespread effects within the population as a whole. By defining the strength of the promoters encoded by the eight subtypes of Correia ends, we provide a resource that allows the transcriptional effects of a particular subtype at a given locus to be predicted.
脑膜炎奈瑟菌是细菌性脑膜炎的主要病原体。该基因组富含重复 DNA，几乎 2%的部分被一种称为科雷亚元件的微小转座子占据。在这里，我们报告了一项生物信息学分析，定义了该元件的 8 种亚型，具有 4 种不同类型的末端。使用 PCR 和 lacZ 报告系统进行的转录分析表明，特别是两个末端编码了强启动子。该元件右端的一个反复出现的多态性（Y128）决定了最强启动子的活性。我们强调了一些似乎驱动邻近基因转录的元件的例子，以及其他可能表达小非编码 RNA 的元件。在三个脑膜炎球菌基因组之间的两两比较中，发现没有超过三分之二的科雷亚元件在任何特定位置保持其亚型。这是由于单个菌株中元件之间的重组类别转换所致。在转换亚型时，一个新的等位基因可以通过自然转化在种群中传播。这个过程可能代表了脑膜炎球菌中相位变异的一个以前未被认识的机制。我们得出结论，科雷亚元件的菌株间可变性以及它们编码的大量强启动子允许整个种群中产生潜在的广泛影响。通过定义科雷亚末端的 8 种亚型编码的启动子的强度，我们提供了一种资源，可以预测特定亚型在特定基因座的转录效应。
