Shotgun EM of mycobacterial protein complexes during stationary phase stress.
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ABSTRACT:
SUBMITTER: Kirykowicz AM
PROVIDER: S-EPMC8244302 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:The majority of active tuberculosis cases arise as a result of reactivation of latent organisms which are quiescent within the host. The ability of mycobacteria to survive extended periods without active replication is a complex process whose details await elucidation. We used two-dimensional gel electrophoresis to examine both steady-state protein composition and time-dependent protein synthetic profiles in aging cultures of virulent Mycobacterium tuberculosis. At least seven proteins were maximally synthesized 1 to 2 weeks following the end of log-phase growth. One of these proteins accumulated to become a predominant stationary-phase protein. N-terminal amino acid sequencing and immunoreactivity identified this protein as the 16-kDa alpha-crystallin-like small heat shock protein. The gene for this protein was shown to be limited to the slowly growing M. tuberculosis complex of organisms as assessed by Southern blotting. Overexpression of this protein in wild-type M. tuberculosis resulted in a slower decline in viability following the end of log-phase growth. Accumulation of this protein was observed in log-phase cultures following a shift to oxygen-limiting conditions but not by other external stimuli. The protein was purified to homogeneity from overexpressing M. smegmatis in two steps and shown to have a significant ability to suppress the thermal denaturation of alcohol dehydrogenase. Collectively, these results suggest that the mycobacterial alpha-crystallin protein may play a role in enhancing long-term protein stability and therefore long-term survival of M. tuberculosis.
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Project description:Background: As carbon sources are exhausted, Saccharomyces cerevisiae cells exhibit reduced metabolic activity and cultures enter stationary phase. We asked whether cells in stationary-phase cultures respond to additional stress at the level of transcript abundance. Results: Microarrays were used to quantify changes in transcript abundance in cells from stationary-phase cultures. In response to oxidative stress, more than 800 mRNAs increased within 1 minute. A significant number of these mRNAs encode proteins involved in stress responses. We tested whether mRNA increases were due to new transcription, rapid poly-adenylation of message (which would not be detected by microarrays), or potential release of mature mRNA sequestered in the cell but insoluble during RNA isolation. Examination of the response to oxidative stress in an RNA polymerase II mutant, rpb1-1 suggested new transcription was not required. Quantitative RT-PCR analysis of a subset of these transcripts further suggested that essentially all isolated transcripts were polyadenylated. In contrast, over 1000 transcripts increased after protease treatment of cell-free lysates from stationary-phase but not exponentially growing cultures. We also determined that oxidative stress and temperature upshift led to the release of different transcripts, suggesting that mRNA release is stress specific. Conclusions: A large number of mRNAs are sequestered in a protease-labile, rapidly releasable form in cells in stationary-phase cultures but not exponentially growing cultures. The differences between mRNAs released by protease treatment and those observed with oxidative stress and temperature upshift, suggest different stresses cause the release of different transcripts. We hypothesize that P-bodies are involved in this sequestration. Keywords: stress response
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Project description:Bacterial ribosomes contain over 50 ribosome core proteins (r-proteins). Tens of non-ribosomal proteins bind to ribosomes to promote various steps of translation or suppress protein synthesis during ribosome hibernation. This study sets out to determine how translation activity is regulated during the prolonged stationary phase. Here, we report the protein composition of ribosomes during the stationary phase. According to quantitative mass-spectrometry analysis, ribosome core proteins bL31B and bL36B are present during the late log and first days of the stationary phase and are replaced by corresponding A paralogs later in the prolonged stationary phase. Ribosome hibernation factors Rmf, Hpf, RaiA, and Sra are bound to the ribosomes during the onset and a few first days of the stationary phase when translation is strongly suppressed. In the prolonged stationary phase, a decrease in ribosome concentration is accompanied by an increase in translation and association of translation factors with simultaneous dissociation of ribosome hibernating factors. The dynamics of ribosome-associated proteins partially explain the changes in translation activity during the stationary phase.
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Project description:To determine where Tup1 binds to chromatin during log phase, diauxic shift and stationary phase, we performed ChIP-seq.
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