Conditional protein splicing of the Mycobacterium tuberculosis RecA intein in its native host

• Published in: Scientific reports Vol. 14; no. 1; pp. 20664 - 14
• Main Authors: Schneider, Ryan F, Hallstrom, Kelly, DeMott, Christopher, McDonough, Kathleen A
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 05.09.2024; Nature Portfolio
• Subjects: Amino acid sequence; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; DNA Damage; DNA damage repair; E coli; Ectopic expression; Environmental effects; Escherichia coli - genetics; Escherichia coli - metabolism; Exaptation; Exteins - genetics; Gene expression; Gene Expression Regulation, Bacterial; Hypoxia; Inteins; Inteins - genetics; Mobile elements; Mycobacterium tuberculosis; Mycobacterium tuberculosis - genetics; Mycobacterium tuberculosis - metabolism; Nucleotide sequence; Post-translational gene regulation; Promoter Regions, Genetic; Proteasome Endopeptidase Complex - genetics; Proteasome Endopeptidase Complex - metabolism; Proteasomes; Protein Splicing; Proteins; Rec A Recombinases - genetics; Rec A Recombinases - metabolism; RecA protein; Recombinase; Serine Endopeptidases; SOS response; Splicing; Tuberculosis; Western blotting; DNA damage repair; Post-translational gene regulation; Exaptation; SOS response; Gene expression; Mobile elements
• DOI: 10.1038/s41598-024-71248-y
• ISSN: 2045-2322

The recA gene, encoding Recombinase A (RecA) is one of three Mycobacterium tuberculosis (Mtb) genes encoding an in-frame intervening protein sequence (intein) that must splice out of precursor host protein to produce functional protein. Ongoing debate about whether inteins function solely as selfish genetic elements or benefit their host cells requires understanding of interplay between inteins and their hosts. We measured environmental effects on native RecA intein splicing within Mtb using a combination of western blots and promoter reporter assays. RecA splicing was stimulated in bacteria exposed to DNA damaging agents or by treatment with copper in hypoxic, but not normoxic, conditions. Spliced RecA was processed by the Mtb proteasome, while free intein was degraded efficiently by other unknown mechanisms. Unspliced precursor protein was not observed within Mtb despite its accumulation during ectopic expression of Mtb recA within E. coli. Surprisingly, Mtb produced free N-extein in some conditions, and ectopic expression of Mtb N-extein activated LexA in E. coli. These results demonstrate that the bacterial environment greatly impacts RecA splicing in Mtb, underscoring the importance of studying intein splicing in native host environments and raising the exciting possibility of intein splicing as a novel regulatory mechanism in Mtb.