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A strand-specific endonucleolytic activity with DNA site preference for cleavage in Chlamydia trachomatis
1Menzies School of Health Research, Darwin, Australia.
Journal of Bacteriology
|August 1, 1994
Summary
Chlamydia trachomatis possesses an endonucleolytic enzyme that specifically cleaves one DNA strand within a key promoter region. This enzyme targets the nontemplate strand, crucial for regulating plasmid-based RNA synthesis.
Area of Science:
- Molecular Biology
- Microbiology
- Enzymology
Background:
- Chlamydia trachomatis is an obligate intracellular bacterium with a unique biology.
- Plasmid-encoded genes regulate essential functions in Chlamydia trachomatis.
- Understanding DNA-modifying enzymes in Chlamydia is key to deciphering its gene regulation.
Purpose of the Study:
- To investigate the presence and characteristics of nucleolytic activities in Chlamydia trachomatis.
- To determine the substrate specificity of any detected endonucleolytic activity.
- To identify the DNA strand targeted by the enzyme within a specific promoter region.
Main Methods:
- Preparation of high-salt extracts from Chlamydia trachomatis cell lysates.
- Assay of endonucleolytic activity using PCR-amplified DNA fragments and supercoiled DNA.
- Analysis of DNA cleavage products to determine strand specificity and identify nick sites.
Main Results:
- Endonucleolytic activity was detected in Chlamydia trachomatis high-salt extracts.
- The enzyme exhibited specificity for one strand of a PCR fragment containing a strong chlamydial promoter.
- This strand-specific cleavage was also observed on supercoiled DNA, targeting the nontemplate strand for two short RNAs.
Conclusions:
- Chlamydia trachomatis possesses a DNA endonuclease with specific strand cleavage activity.
- The enzyme targets the nontemplate strand of a promoter regulating plasmid-specified RNAs.
- Sequence analysis suggests a consensus motif may be involved in enzyme recognition.