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Origin recognition specificity in pT181 plasmids is determined by a functionally asymmetric palindromic DNA element
P Z Wang1, S J Projan, V Henriquez
1Department of Plasmid Biology and Applied Genetics, Public Health Research Institute of the City of New York, Inc., NY 10016.
The EMBO Journal
|January 1, 1993
Summary
The pT181 plasmid replication origin uses two repeats (IR-II and IR-III) for initiator protein (Rep) binding. Specific sequences in IR-III are crucial for recognition, with unique DNA-protein interactions proposed.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- The pT181 plasmid's leading strand replication origin involves two adjacent inverted repeat elements, IR-II and IR-III.
- These elements are critical for recognition by the initiator (Rep) protein, a key factor in rolling circle replication.
Purpose of the Study:
- To elucidate the specific roles of IR-II and IR-III in Rep protein binding and origin recognition.
- To investigate the DNA-protein interactions governing the specificity and efficiency of replication initiation.
Main Methods:
- Genetic analysis to determine the functional importance of different DNA regions within IR-III.
- Analysis of DNA-protein interactions, including the role of the Rep protein dimer.
Main Results:
- The distal arm of IR-III is not essential for sequence-specific recognition, unlike the proximal arm and central region.
- The spacing and phasing between IR-II and IR-III are critical for origin function.
- A unique DNA-protein interaction model is proposed, involving symmetrical binding of the dimeric Rep protein to IR-III, influenced by adjacent IR-II.
Conclusions:
- The central segment of IR-III likely positions Rep for optimal interaction with flanking half-sites.
- The interaction between Rep and the origin elements is complex, involving sequence-specific and non-specific recognition modulated by DNA structure and protein dimerization.