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Nucleotide sequence analysis of RepFIC, a basic replicon present in IncFI plasmids P307 and F, and its relation to
Abstract:
RepFIC is a basic replicon of IncFI plasmid P307 which is located within a 3.09-kilobase SmaI fragment. The nucleotide sequence of this region has been determined and shown to be homologous with the RepFIIA replicon of IncFII plasmids. The two replicons share three homologous regions, HRI, HRII, and HRIII, which are flanked by two nonhomologous regions, NHRI and NHRII. A comparison of coding regions reveals that the two replicons have several features in common. RepFIC, like RepFIIA, codes for a repA2 protein with its amino-terminal codons in HRI and its carboxy-terminal codons in NHRI. Although the codons for the repA1 proteins are located in NHRII, the DNA region containing a putative promoter, ribosomal binding site, and initiation codons is located in HRII. This region also codes for an inc RNA. There are nine base-pair differences between the inc RNA of RepFIIA and that of RepFIC, and as a result, RepFIC and RepFIIA replicons are compatible. An EcoRI fragment from the F plasmid which shows homology with RepFIC of P307 has also been sequenced. This fragment contains only a portion of RepFIC, including the genes for the putative repA2 protein and inc RNA. The region coding for a putative repA1 protein is interrupted by the transposon Tn1000 and shows no homology with the repA1 region of RepFIIA and RepFIC of P307. Our comparative and structural analyses suggest that RepFIC and RepFIIA, although different, have a similar replication mechanism and thus can be assigned to the same replicon family, which we designate the RepFIIA family.
Insights
The RepFIC and RepFIIA replicons share homologous regions and coding features, enabling similar replication mechanisms. These findings establish them as part of the same RepFIIA replicon family.
Area of Science:
- Molecular Biology
- Genetics
- Plasmid Biology
Background:
- RepFIC is a basic replicon from IncFI plasmid P307.
- IncFII plasmids contain the homologous RepFIIA replicon.
Purpose of the Study:
- To determine the nucleotide sequence of the RepFIC basic replicon.
- To compare RepFIC with the RepFIIA replicon for structural and functional similarities.
- To investigate the compatibility between RepFIC and RepFIIA replicons.
Main Methods:
- DNA sequencing of the RepFIC basic replicon.
- Comparative analysis of nucleotide sequences and coding regions between RepFIC and RepFIIA.
- Analysis of inc RNA sequences and potential promoter regions.
Main Results:
- RepFIC and RepFIIA share homologous regions (HRI, HRII, HRIII) and nonhomologous regions (NHRI, NHRII).
- Both replicons encode a repA2 protein and an inc RNA, with RepFIC and RepFIIA inc RNAs differing by nine base pairs, ensuring compatibility.
- A fragment of RepFIC from the F plasmid contains repA2 and inc RNA genes, but the repA1 gene is interrupted by Tn1000.
Conclusions:
- RepFIC and RepFIIA possess similar replication mechanisms despite structural differences.
- RepFIC and RepFIIA belong to the same replicon family, designated the RepFIIA family.