Nucleotide sequence and replication characteristics of RepHI1B: a replicon specific to the IncHI1 plasmids
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P Gabant1, A O Chahdi, M Couturier
1Département de Biologie Moléculaire, Université Libre de Bruxelles, Rhode Saint Genèse, Belgium.
Abstract:
The IncHI1 plasmids are multireplicon plasmids. They contain at least three autoreplicative regions, one of which is closely related to the RepFIA replicon of F. Two other IncHI1-specific replicons, RepHI1A and RepHI1B, have been recently isolated and mapped on the R27 (IncHI1) genome (P. Gabant, P. Newnham, D. Taylor, and M. Couturier, J. Bacteriol. 175, 7697-7701, 1993). In the present work, the DNA sequence of RepHI1B was determined. It reveals DNA repeats of 17 base pairs located upstream and downstream from a gene coding for a 32 kilodalton protein (RepA) required for replication. Interestingly, RepA presents significant homology with other Rep proteins encoded by plasmids belonging to different incompatibility groups: P1 (IncY), Rts1 (IncT), RepFIB (IncFI) and RepHI1A (IncHI1). All these results provide strong evidence that the RepHI1B replicon of the IncHI1 subgroup belongs to the group of plasmids which control their copy number by an iteron mechanism.
Insights
The IncHI1 plasmid RepHI1B replicon was sequenced, revealing DNA repeats and a replication protein (RepA). This protein shows homology to others, suggesting IncHI1 plasmids use an iteron mechanism for copy number control.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- IncHI1 plasmids are multireplicon plasmids with multiple autoreplicative regions.
- Two IncHI1-specific replicons, RepHI1A and RepHI1B, have been identified on the R27 genome.
Purpose of the Study:
- To determine the DNA sequence of the RepHI1B replicon.
- To investigate the replication mechanism of IncHI1 plasmids.
Main Methods:
- DNA sequencing of the RepHI1B replicon.
- Bioinformatic analysis of the DNA sequence and encoded protein.
Main Results:
- The RepHI1B sequence contains 17 base pair repeats flanking a gene encoding a 32 kDa replication protein (RepA).
- The RepA protein exhibits significant homology to Rep proteins from plasmids of different incompatibility groups (IncY, IncT, IncFI, IncHI1).
Conclusions:
- The RepHI1B replicon of IncHI1 plasmids likely utilizes an iteron mechanism for copy number control.
- The homology of RepA suggests a conserved replication strategy among diverse plasmid groups.