Two discrete elements are required for the replication of a repABC plasmid:: an antisense RNA and a stem-loop structure
Two discrete elements are required for the replication of a repABC plasmid:: an antisense RNA and a stem-loop structure
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DOI：
10.1111/j.1365-2958.2004.04366.x
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发表时间：
2004-12-01
影响因子：
3.6
通讯作者：
Cevallos, MA
中科院分区：
文献类型：
--
作者：
Venkova-Canova, T;Soberón, NE;Cevallos, MA
EpABC复制子含有一个操纵子，编码启动子蛋白(RepC)和分割蛋白(RepA和RepB)。后两种蛋白质负调控操纵子的转录。在这篇文章中，我们鉴定了两个新的调控元件，它们位于保守的epB-epC基因间隔区序列中，它们负向调控着等根瘤菌p42d质粒中epC的表达。其中一个是小的反义RNA，另一个是refABC mRNA中的茎环结构，它封闭了repC的Shine-Dalgarno序列。根据体内和体外的分析，小的反义RNA(57-59nt)类似于典型的复制负调控因子，因为：(I)它是从强构成启动子(P2)转录而来的，(Ii)转录本与RepC编码序列上游的非翻译区重叠，(Iii)RNA形成一个二级结构，作为Rho非依赖的终止子，(Iv)反义RNA是一个强大的反式不相容因子，(V)它的存在降低了RepC的表达水平。令人惊讶的是，这两个看似负的调控因子都是有效的质粒复制所必需的。
The repABC replicons contain an operon encoding the initiator protein (RepC) and partitioning proteins (RepA and RepB). The latter two proteins negatively regulate the transcription of the operon. In this article we have identified two novel regulatory elements, located within the conserved repB-repC intergenic sequence, which negatively modulate the expression of repC, in plasmid p42d of Rhizobium etli. One of them is a small antisense RNA and the other is a stem-loop structure in the repABC mRNA that occludes the Shine-Dalgarno sequence of repC. According to in vivo and in vitro analyses, the small antisense RNA (57-59 nt) resembles canonical negative regulators of replication because: (i) it is transcribed from a strong constitutive promoter (P2), (ii) the transcript overlaps untranslated region upstream of the RepC coding sequences, (iii) the RNA forms one secondary structure acting as a rho-independent terminator, (iv) the antisense RNA is a strong trans-incompatibility factor and (v) its presence reduces the level of repC expression. Surprisingly, both of these seemingly negative regulators are required for efficient plasmid replication.