Snyder Lori A S, Cole Jeff A, Pallen Mark J
Systems Biology, University of Birmingham, Edgbaston, Birmingham, UK.
BMC Genomics. 2009 Feb 9;10:70. doi: 10.1186/1471-2164-10-70.
The Correia Repeat Enclosed Element (CREE) of the Neisseria spp., with its inverted repeat and conserved core structure, can generate a promoter sequence at either or both ends, can bind IHF, and can bind RNase III and either be cleaved by it or protected by it. As such, the presence of this element can directly control the expression of adjacent genes. Previous work has shown differences in regulation of gene expression between neisserial strains and species due to the presence of a CREE. These interruptions perhaps remove the expression of CREE-associated genes from ancestral neisserial regulatory networks.
Analysis of the chromosomal locations of the CREE in Neisseria gonorrhoeae strain FA1090 and N. gonorrhoeae strain NCCP11945 has revealed that most of the over 120 copies of the element are conserved in location between these genome sequences. However, there are some notable exceptions, including differences in the presence and sequence of CREE 5' of copies of the opacity protein gene opa, differences in the potential to bind IHF, and differences in the potential to be cleaved by RNase III.
The presence of CREE insertions in one strain relative to the other, CREE within a prophage region, and CREE disrupting coding sequences, provide strong evidence of mobility of this element in N. gonorrhoeae. Due to the previously demonstrated role of these elements in altering transcriptional control and the findings from comparing the two gonococcal genome sequences, it is suggested that regulatory differences orchestrated by CREE contribute to the differences between strains and also between the closely related yet clinically distinct species N. gonorrhoeae, Neisseria meningitidis, and Neisseria lactamica.
淋病奈瑟菌属的科雷亚重复封闭元件（CREE）具有反向重复序列和保守的核心结构，可在其一端或两端产生启动子序列，能结合整合宿主因子（IHF），还能结合核糖核酸酶III（RNase III），并可被其切割或受其保护。因此，该元件的存在可直接控制相邻基因的表达。先前的研究表明，由于CREE的存在，淋病奈瑟菌菌株和种之间在基因表达调控上存在差异。这些中断可能使CREE相关基因的表达从淋病奈瑟菌的祖先调控网络中消失。
对淋病奈瑟菌菌株FA1090和淋病奈瑟菌菌株NCCP11945中CREE的染色体定位分析表明，该元件的120多个拷贝中的大多数在这些基因组序列之间的位置是保守的。然而，也有一些明显的例外，包括不透明蛋白基因opa拷贝的CREE 5'端在存在和序列上的差异、结合IHF的潜力差异以及被RNase III切割的潜力差异。
相对于另一个菌株，一个菌株中存在CREE插入、原噬菌体区域内的CREE以及破坏编码序列的CREE，为该元件在淋病奈瑟菌中的移动性提供了有力证据。由于先前已证明这些元件在改变转录控制方面的作用以及比较两个淋球菌基因组序列的结果，表明由CREE精心策划的调控差异导致了菌株之间以及密切相关但临床特征不同的物种淋病奈瑟菌、脑膜炎奈瑟菌和乳糖奈瑟菌之间的差异。
