The Mycobacterium tuberculosis CRISPR-Associated Cas1 Involves Persistence and Tolerance to Anti-Tubercular Drugs

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• Tuberculosis (TB) is a major global health threat, with drug-resistant strains posing a significant challenge.
• The CRISPR-associated protein 1 (Cas1) is crucial for spacer integration in CRISPR arrays and its deletion is observed in drug-resistant TB.
• The specific role of Cas1 in the Mycobacterium type III-A CRISPR system remains largely uncharacterized.

Purpose of the Study:

• To investigate the function of Cas1 (Rv2817c) in Mycobacterium tuberculosis complex (MTBC) drug resistance.
• To explore Cas1's role in new spacer acquisition and its impact on bacterial persistence and stress response.

Main Methods:

• Analysis of Cas1 deletion in clinical TB isolates.
• Challenging Bacillus Calmette-Guérin (BCG) with mycobacteriophage D29 to assess spacer acquisition.
• Expression of Cas1 in recombinant Mycobacterium smegmatis to evaluate drug sensitivity, DNA repair, and stress response.

Main Results:

• Cas1 deletion was detected in 57.14% of clinical isolates.
• No newly acquired spacer sequences matching the D29 genome were identified in BCG.
• Recombinant Cas1 expression in M. smegmatis increased sensitivity to anti-TB drugs by reducing bacterial persistence, impaired DNA repair, and altered stress responses.

Conclusions:

• Cas1 plays a significant role in MTBC drug resistance evolution.
• Cas1's function in impairing DNA repair and altering stress responses contributes to increased drug sensitivity.
• Understanding Cas1's role offers new therapeutic strategies for tuberculosis treatment.