| Project Detail |
Protein homeostasis, comprising as a key element the controlled degradation of proteins by multi-subunit protease machines, plays a central role in bacterial adaptation. Mycobacteria have obtained proteasomes by horizontal gene transfer that support their survival in adverse environments, like for example under DNA damaging conditions or during persistence of Mycobacterium tuberculosis in human macrophages. Proteins are marked for proteasomal degradation by post-translational modification with the small protein Pup (prokaryotic ubiquitin-like protein). Pupylated proteins are recognized by the mycobacterial proteasomal ATPase (Mpa) that associates with the 20S proteasome to fuel their processive degradation. Pupylation and proteasomal degradation play a key role in the mycobacterial DNA damage response, since RecA, the protein that acts as co-activator and stress-sensor in the SOS response, as well as many DNA repair proteins are controlled by pupylation. Further underscoring the importance of the Pup-proteasome system (PPS) during DNA damage, the key transcriptional activator of the mycobacterial DNA damage response, proteasome accessory factor BC (PafBC) is encoded in the PPS gene locus. PafBC controls a regulon of around 150 genes and also co-regulates the SOS response. We discovered that this heterodimeric transcriptional regulator employs a unique mode of promoter recognition that we termed ‘sigma adaptation’, as it enables housekeeping RNA polymerase holoenzyme to switch to the transcription of DNA stress response genes. Here, we propose to use a combination of cellular, biochemical and single-molecule experiments to gain a molecular understanding of the protein degradation and regulatory pathways involved in controlling protein homeostasis during DNA damage stress. |
