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Critical sequences in the core of the P1 plasmid replication origin
T Brendler1, A Abeles, S Austin
1Laboratory of Chromosome Biology, NCI-Frederick Cancer Research and Development Center, Maryland 21702.
Journal of Bacteriology
|July 1, 1991
Summary
The P1 plasmid replication origin requires specific 7-bp repeats for function. Mutations within these repeats, not just GATC methylation, can block replication initiation.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The P1 plasmid replication origin is crucial for its propagation.
- Its core structure involves 7-bp repeats and a G+C-rich region.
- Methylation of GATC sequences within the repeats is known to be essential.
Purpose of the Study:
- To investigate the functional importance of the P1 plasmid replication origin's core elements.
- To determine the impact of single-base mutations on origin function.
- To elucidate the roles of the 7-bp repeats and the G+C-rich region.
Main Methods:
- Isolation and characterization of forty single-base mutations within the P1 origin region.
- Assay of mutated origins for replication function.
- Analysis of mutation effects on repeat integrity and G+C-rich region spacing.
Main Results:
- Single-base changes within any 7-bp repeat abolished origin function, regardless of GATC methylation status.
- The 7-bp repeats are critical, while the inter-repeat intervals are not.
- The G+C-rich region acts as a spacer, with length being critical but sequence less so, maintaining distance to RepA binding sites.
Conclusions:
- The structural integrity of the 7-bp repeats is paramount for P1 plasmid origin function.
- The G+C-rich region serves as a critical spacer, influencing initiator protein binding and potentially DNA strand separation.
- Replication initiation is sensitive to precise repeat sequences, highlighting a complex regulatory mechanism beyond simple methylation.