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Size variation in group A streptococcal M protein is generated by homologous recombination between intragenic repeats
Abstract:
M protein, a major surface protein and virulence factor for the group A streptococcus, exhibits extraordinary size variation in strains of the same serotype (Fischetti et al. 1985). RNA sequence analysis of spontaneous M protein size variants shows that deletion mutations arise in a single strain by homologous recombination events between intragenic tandem repeats. Similar deletion and duplication events also occur in serial streptococcal isolates from a single patient and among related strains in a recent outbreak. We discuss how homologous recombination events can lead to the generation of antigenic variation.
Insights
Group A Streptococcus M protein size variation is caused by gene mutations. Homologous recombination between tandem repeats leads to deletions and duplications, driving antigenic variation.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Group A Streptococcus (GAS) M protein is a major surface protein and virulence factor.
- GAS M protein exhibits significant size variation within the same serotype.
Purpose of the Study:
- To investigate the molecular mechanisms underlying M protein size variation in GAS.
- To understand how genetic events contribute to antigenic variation in GAS.
Main Methods:
- RNA sequence analysis of spontaneous M protein size variants.
- Examination of deletion and duplication events in serial isolates and outbreak strains.
Main Results:
- Deletion mutations in M protein arise via homologous recombination between intragenic tandem repeats.
- Similar deletion and duplication events were observed in serial isolates from a single patient.
- These genetic events were also found among related strains in a recent outbreak.
Conclusions:
- Homologous recombination involving intragenic tandem repeats is a key mechanism for generating M protein size variation.
- This variation contributes to the antigenic diversity of Group A Streptococcus, potentially aiding immune evasion.