Regulatory interactions between RepA, an essential replication protein, and the DNA repeats of RepFIB from plasmid P307

Abstract

The control of RepFIB replication appears to rely on the interaction between an initiator protein (RepA) and two sets of DNA repeat elements located on either side of the repA gene (BCDD'D" and EFGHIJ). In vivo genetic tests demonstrate that the BCDD'D" repeats form part of the origin of replication, while some of the downstream repeat elements (HIJ) are involved in the sensing and setting of plasmid copy number. RepA DNA binding to these groups of repeats has been investigated in vivo by utilizing the fact that the replicon contains three active promoters (orip, repAp, and EFp), one of which has previously been shown to control the expression of repA (repAp). All three promoters are closely associated with the repeat elements flanking repA, and an investigation using lacZ or cml gene fusions has demonstrated that RepA expressed in trans is able to repress each promoter. However, these assays suggest that the transcriptional responses of orip and repAp to RepA repression are significantly different, despite the fact that both promoters are embedded within the BCDD'D" repeat elements. Extra copies of the BCDD'D" or EFG repeats in trans have no effect on RepA repression of repAp embedded in a second copy of the BCDD'D" repeats, but copies of the HIJ or EFGHIJ repeats are able to derepress repAp, suggesting that there is a fundamental difference between RepA-BCDD'D" or -HIJ complexes and RepA-EFG or -EFGHIJ complexes.

Global Distribution and Diversity of Prevalent Sewage Water Plasmidomes

“…Replication group 1 contained domains for rolling circle initiator proteins (Rep_1 [ 41 ], Rep_2 [ 42 , 43 ], RepL [ 44 , 45 ], and the excluded Rep_trans [ 46 ]), while groups 2 and 3 contained domains of theta replication initiators (Rep_3 [ 47 , 48 ] and Replicase [ 49 ]). Therefore, it makes sense that the group 1 replication domains are the ones that are the most entangled with bacteriophages, which also use rolling circle replication ( 50 ).…”

Global distribution and diversity of prevalent sewage water plasmidomes

“…Replication group 1 contained domains for rolling circle initiator proteins (Rep_1 55 , Rep_2 56,57 , RepL 58,59 , and the exluded Rep_trans 60 ), while groups 2 and 3 contain domains of theta replication initiators (Rep_3 61,62 and Replicase 63 ). It therefore makes sense that group 1 replication domains are the ones that are the most entangled with bacteriophages, which also use rolling circle replication 8 .…”

Molecular analysis of RepHI1B, a replicon specific to IncHI1 plasmids

“…In several other replicons related to RepHI1B, the operator/promoter of the gene coding for the initiator protein has likewise been located in the origin of replication. These include P1 (Chattoraj et al 1985), RepFIB (Spiers et al 1993), Rts1 (Itoh et al 1987), and RepHI1A (Newnham and Taylor 1994). In the case of P1, it has been shown that it is the monomeric form of RepA that binds all the repeats (Wickner et al 1991).…”