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H-DNA formation by the coding repeat elements of neisserial opa genes
1Laboratory of Microbial Structure and Function, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rocky Mountain Laboratories, Hamilton, Montana 59840.
Molecular Microbiology
|October 1, 1991
Summary
The opa gene coding repeat regions in Neisseria form H-DNA structures, influencing gene expression through repeat additions/deletions. This bacterial H-DNA is unique, residing within the gene
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Opa genes in Neisseria gonorrhoeae and Neisseria meningitidis regulate gene expression via pentanucleotide coding repeat (CR) unit dynamics.
- CR units (CTTCT) undergo high-frequency addition and deletion, impacting gene expression states.
Purpose of the Study:
- To investigate the in vitro structural properties of opa gene CR regions.
- To determine the role of these structures in bacterial gene phase variation.
Main Methods:
- In vitro analyses using single-strand specific nucleases and oligonucleotide protection experiments.
- Assessment of non-B-DNA residue modifications.
- Construction of beta-galactosidase::CR translational fusions to study phase variation.
Main Results:
- Opa gene CR regions form H-DNA structures under acidic conditions with negative supercoiling.
- The purine/pyrimidine strand bias and H-palindromic nature support H-DNA formation.
- Flanking sequences are necessary for in vitro H-DNA formation, as shown by translational fusions exhibiting phase variation.
Conclusions:
- The opa gene CR region represents the first identified bacterial H-DNA structure.
- This unique H-DNA structure is located within the coding sequence of the gene.
- H-DNA formation and CR dynamics are key mechanisms for opa gene phase variation.