Project description:The major human pathogen Mycobacterium tuberculosis can survive in the host organism for decades without causing symptoms. A large cohort of Toxin-Antitoxin (TA) modules contribute to this persistence. Of these, 48 TA modules belong to the vapBC (virulence associated protein) gene family. VapC toxins are PIN domain endonucleases that, in Enterobacteria, inhibit translation by site-specific cleavage of initiator tRNA. In contrast, VapC20 of M. tuberculosis inhibits translation by site-specific cleavage of the universally conserved Sarcin-Ricin loop (SRL) in 23S rRNA. Here we identify cleavage targets for 12 VapCs from M. tuberculosis by applying UV-crosslinking and deep sequencing. Remarkably, these VapCs are all endoribo-nucleases that cleave RNA targets that are essential for decoding at the ribosomal A-site. Eleven VapCs cleave specific tRNAs while one exhibits SRL cleavage activity. These findings suggest that multiple vapBC modules contribute to the survival of M. tuberculosis in its human host by reducing the level of translation.
Project description:Tuberculosis is a leading cause of worldwide infectious mortality. The prevalence of multidrug-resistant Mycobacterium tuberculosis (Mtb) infections drives an urgent need to exploit new drug targets. One such target is the ATP-dependent protease ClpC1P1P2, which is strictly essential for viability. However, few proteolytic substrates of mycobacterial ClpC1P1P2 have been identified to date. Recent studies in Bacillus subtilis have shown that the orthologous ClpCP protease recognizes proteolytic substrates bearing post-translational arginine phosphorylation. While several lines of evidence suggest that ClpC1P1P2 is similarly capable of recognizing phosphoarginine-bearing proteins, the existence of phosphoarginine modifications in mycobacteria has remained in question. Here, we confirm the presence of post-translational phosphoarginine modifications in Mycolicibacterium smegmatis (Msm), a nonpathogenic surrogate of Mtb. Using a phosphopeptide enrichment workflow coupled with shotgun phosphoproteomics, we identify arginine phosphosites on several functionally diverse targets within the Msm proteome. Interestingly, phosphoarginine modifications are not upregulated by heat stress, suggesting divergent roles in mycobacteria and Bacillus. Our findings provide new evidence supporting the existence of phosphoarginine-mediated proteolysis by ClpC1P1P2 in mycobacteria and other actinobacterial species.
Project description:Tuberculosis remains a leading cause of worldwide infectious mortality and one of the top ten leading causes of death overall. While advances in public health have contributed to a reduction in tuberculosis cases, the prevalence of multidrug-resistant Mycobacterium tuberculosis (Mtb) (MDR-TB) infections has created an urgent need to exploit novel drug targets. One such target is the ClpC1P1P2 protease, which degrades folded cytosolic proteins through the cooperation of the ATP-dependent unfoldase ClpC1 and the ClpP1P2 peptidase. Both protease components are strictly essential for Mtb viability and are validated therapeutic targets. However, efforts to develop anti-Mtb compounds are constrained by a limited understanding of Clp protease function and essentiality. Thus, it is crucial to identify physiological substrates and pathways regulated by this protease. In this study, we identify cellular proteins that interact with the ClpC1 unfoldase in Mycolicibacterium smegmatis (Msm), a nonpathogenic surrogate for Mtb. Using a FLAG-tagged ClpC1 variant with mutations within the Walker B motifs, candidate ClpC1 interaction partners were captured by co-immunoprecipitation and identified by mass spectrometry-based proteomics (LC-MS/MS). Notably, our work reveals a novel proteolytic substrate, 5-oxoprolinase, which is recognized by ClpC1P1P2 via an N-terminal degradation sequence.
Project description:RNA-seq of Mycobacteriophage Island3 infection of Mycolicibacterium smegmatis mc2155, Mycolicibacterium smegmatis mc2155(Butters), and Mycolicibacterium smegmatis mc2155(Buttersgp57r) to assess the impact of Butters lysogen and specifically Buttersgp57r on transcript levels of island3 during infection.