Control of ColE1 DNA replication: the rop gene product negatively affects transcription from the replication primer promoter.

Publisher Website
Google Scholar
Abstract
A 600-base-pair region essential for ColE1 and pMB1 plasmid replication [in Escherichia coli] contains 2 promoters responsible for the synthesis of 2 RNA molecules central to copy number control. One promoter directs synthesis of the primer RNA precursor. The 2nd promoter directs the synthesis of a small RNA molecule, RNA1, which acts in trans to inhibit processing of the RNA primer precursor. Each promoter was fused to the .beta.-galactosidase structural gene contained in a .lambda. phage. Expression of the RNA1 promoter in lysogens is not influenced by the presence of wild-type pMB1 or ColE1 plasmids residing in the cell. Transcription from the RNA primer promoter, however, is repressed by the product of a trans-acting plasmid gene product, which was designated rop (for repressor of primer). The rop gene maps downstream from the replication origin in a region that encodes a polypeptide of 63 amino acids whose sequence is completely conserved in pMB1 and ColE1. This polypeptide is probably the rop gene product and it may regulate plasmid DNA replication by modulating the initiation of transcription of the primer RNA precursor.