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Linear Streptomyces plasmids form superhelical circles through interactions between their terminal proteins
Hsiu-Hui Tsai1, Chih-Hung Huang, Ingrid Tessmer
1Department of Life Sciences and Institute of Genome Sciences, National Yang-Ming University, Shih-Pai, Taipei 112, Taiwan.
Nucleic Acids Research
|November 27, 2010
Summary
Terminal proteins (TPs) on Streptomyces linear DNA interact within and between molecules. These interactions create superhelicity, complicating DNA replication and requiring resolution.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Streptomyces linear chromosomes and plasmids have terminal proteins (TPs) at telomeres.
- TPs are crucial for DNA replication, acting as primers for gap filling.
- Archetypal TPs (Tpg) are conserved, while atypical TPs (like Tpc) vary in sequence and size.
Purpose of the Study:
- To investigate in vivo interactions between terminal proteins (TPs) in Streptomyces.
- To determine if interactions occur between TPs on the same DNA molecule (intramolecular) or different molecules (intermolecular).
- To explore interactions between TPs on chromosomal and plasmid telomeres.
Main Methods:
- Chemical cross-linking was employed to detect and analyze TP interactions in vivo.
- Electrophoretic behaviors and genetic maps provided prior suggestions of TP interactions.
- Topoisomerase I was used to assess the impact of superhelicity.
Main Results:
- Demonstrated both intramolecular and intermolecular interactions between Tpgs, Tpcs, and between Tpg and Tpc.
- Confirmed interactions between TPs on chromosomal and plasmid telomeres in vivo.
- Observed that intramolecular telomere interactions induce negative superhelicity, which is resolved by topoisomerase I.
Conclusions:
- Terminal proteins (TPs) on Streptomyces linear replicons engage in significant intra- and intermolecular interactions.
- These TP interactions contribute to DNA superhelicity, presenting challenges for post-replicational DNA processing.
- Resolution mechanisms, potentially involving TP or DNA exchange, are necessary to overcome replication complications arising from TP associations.
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