Hill C W, Feulner G, Brody M S, Zhao S, Sadosky A B, Sandt C H
Department of Biochemistry and Molecular Biology, Pennsylvania State University College of Medicine, Hershey 17033, USA.
Genetics. 1995 Sep;141(1):15-24. doi: 10.1093/genetics/141.1.15.
The Rhs family of composite genetic elements was assessed for variation among independent Escherichia coli strains of the ECOR reference collection. The location and content of the RhsA-B-C-F subfamily correlates highly with the clonal structure of the ECOR collection. This correlation exists at several levels: the presence of Rhs core homology in the strain, the location of the Rhs elements present, and the identity of the Rhs core-extensions associated with each element. A provocative finding was that an identical 1518-bp segment, covering core-extension-b1 and its associated downstream open reading frame, is present in two distinct clonal groups, but in association with different Rhs elements. The sequence identity of this segment when contrasted with the divergence of other chromosomal segments suggests that shuffling of Rhs core extensions has been a relatively recent variation. Nevertheless the copies of core-extension-b1 were placed within the respective Rhs elements before the emergence of the clonal groups. In the course of this analysis, two new Rhs elements absent from E. coli K-12 were discovered: RhsF, a fourth member of the RhsA-B-C-F subfamily, and RhsG, the prototype of a third Rhs subfamily.
对复合遗传元件的Rhs家族进行了评估，以了解ECOR参考菌株库中独立大肠杆菌菌株之间的差异。RhsA - B - C - F亚家族的位置和内容与ECOR菌株库的克隆结构高度相关。这种相关性存在于几个层面：菌株中Rhs核心同源性的存在、所存在的Rhs元件的位置以及与每个元件相关的Rhs核心延伸的同一性。一个引人注目的发现是，一个相同的1518 bp片段，涵盖核心延伸 - b1及其相关的下游开放阅读框，存在于两个不同的克隆群中，但与不同的Rhs元件相关。与其他染色体片段的差异相比，该片段的序列同一性表明Rhs核心延伸的重排是一个相对较新的变异。然而，在克隆群出现之前，核心延伸 - b1的拷贝就已被置于各自的Rhs元件内。在该分析过程中，发现了大肠杆菌K - 12中不存在的两个新的Rhs元件：RhsF，RhsA - B - C - F亚家族的第四个成员，以及RhsG，第三个Rhs亚家族的原型。
