Comprehensive analysis of CRISPR array repeat mutations reveals subtype-specific patterns and links to spacer...

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR) and CRISPR-associated (Cas) proteins provide adaptive immunity in prokaryotes.
• CRISPR arrays, composed of repeats and spacers, are essential for recognizing and degrading foreign DNA.
• The mutational dynamics of CRISPR repeat sequences are not well understood, yet are critical for system function.

Purpose of the Study:

• To investigate mutation patterns in CRISPR array repeat sequences across diverse prokaryotic genomes.
• To understand the evolutionary forces shaping repeat sequence integrity and their relationship with spacer dynamics.

Main Methods:

• Analysis of 56,343 CRISPR arrays from 25,628 prokaryotic genomes.
• Comparative assessment of mutation frequencies in terminal versus internal repeat sequences.
• Examination of mutation patterns across different CRISPR subtypes.

Main Results:

• Mutation frequency is significantly higher in terminal repeats compared to internal repeats across all CRISPR system types.
• Unexpected variation in mutation patterns exists among different CRISPR subtypes, indicating diverse evolutionary pressures.
• Hotspots for terminal repeat mutations correlate with regions of high spacer conservation, suggesting a link between repeat mutations and spacer dynamics.

Conclusions:

• CRISPR repeat mutation dynamics are complex and vary significantly across CRISPR subtypes.
• Repeat mutations may influence spacer retention or deletion, highlighting an evolutionary trade-off between CRISPR array stability and adaptability.
• Understanding these dynamics is crucial for deciphering the evolution and function of CRISPR-Cas adaptive immunity.