Ramírez-Romero M A, Téllez-Sosa J, Barrios H, Pérez-Oseguera A, Rosas V, Cevallos M A
Programa de Evolución Molecular, Centro de Investigación sobre Fijación de Nitrógeno, Universidad Nacional Autónoma de México, Apartado Postal 565-A, Cuernavaca, Morelos, México.
Mol Microbiol. 2001 Oct;42(1):195-204. doi: 10.1046/j.1365-2958.2001.02621.x.
The basic replicon of Rhizobium etli CE3, like other members of the repABC plasmid family, is constituted by the repABC operon. RepC is essential for replication, and RepA and RepB play a role in plasmid segregation. It has been shown that deletion derivatives lacking the repAB genes have an increased copy number, indicating that these genes participate in the control of plasmid copy number. RepA is also a trans-incompatibility factor. To understand the regulation of the repABC operon, in this paper: (i) the transcription start site of the repABC operon was determined; (ii) the promoter region was identified by site-directed mutagenesis of the putative -35 and -10 hexameric elements; and (iii) RepA was recognized as a negative regulator of the transcription of the repABC operon.
与repABC质粒家族的其他成员一样，费氏中华根瘤菌CE3的基本复制子由repABC操纵子构成。RepC对复制至关重要，而RepA和RepB在质粒分离中发挥作用。研究表明，缺失repAB基因的缺失衍生物拷贝数增加，这表明这些基因参与了质粒拷贝数的控制。RepA也是一种反式不相容因子。为了理解repABC操纵子的调控机制，本文：（i）确定了repABC操纵子的转录起始位点；（ii）通过对假定的-35和-10六聚体元件进行定点诱变来鉴定启动子区域；（iii）确认RepA是repABC操纵子转录的负调控因子。
