Biology subjects

Fitriasari, S.

Publications and source records attributed to Fitriasari, S..

2 recordsLinked to original sources

bioRxiv2024

The usual and unusual functions of thioredoxins in the metabolism and stress-response of sulfate-reducing bacteria

Thioredoxins are small, universal, disulfide isomerase proteins with required functions in oxidative stress response and RNA synthesis, among others. However, little is known about how anaerobic organisms maintain their intracellular redox balance or how thioredoxins may function differently under anaerobic metabolism. In this study, we investigated the roles of thioredoxins in sulfate-reducing microorganisms (SRMs). SRMs use sulfate as their primary electron acceptor in respiration to produce sulfide and are found in various environments including marine, freshwater sediments, guts and biofilms on ferrous metals where corrosion occurs. We found SRMs lack common redox maintenance molecules and macromolecules but have many and varied thioredoxins belonging to three types. Then, we probed their functions in the model SRM, Desulfovibrio vulgaris Hildenborough (DvH), by an in vivo disulfide bond capture proteomics experiment in both non-stressed and oxidatively stressed conditions. Our results demonstrated that thioredoxin 1 (Trx1) was essential in DvH and selectively responded to oxidative stress. Our data supported its role in RNA synthesis and energy transduction since Trx1 interacted with DsrC and QmoB. Thioredoxin 3 (Trx3), an atypical thioredoxin, was observed to have roles in sulfur transfer and dissimilatory sulfur metabolism. Next, DvH thioredoxin system protein encoding genes were deleted and single deletion mutant strains were tested for growth phenotypes under a variety of different electron donors, acceptors and toxic metal stresses. It is found that dissimilatory sulfate reduction improves resistance of DvH to metal stress. It appeared the sulfide provided certain protection to DvH from silver and uranium stress. ImportanceWe put forth new functions for thioredoxins and a more robust understanding of sulfate reducing microorganisms physiology. Thioredoxin is of general interest because it has been widely studied for redox homeostasis or cancer therapies dealing with the excess of reactive oxygen species (ROS). Our results indicated that these proteins do have functions in stress response, even in microorganisms that generate large amounts of sulfide. We also identified interaction partners for an atypical thioredoxin, suggesting distinct roles from conserved thioredoxin. Mechanisms of metal stress response were found to be different than direct oxidative stress. Thioredoxin did not appear to be involved in uranium reduction electron transfer pathways, contradicting a hypothesis from the literature.

microbiology↗

bioRxiv2021

Dynamic regulation and requirement for ribosomal RNA transcription duringmammalian development

Ribosomal RNA (rRNA) transcription by RNA Polymerase I (Pol I) is a critical rate-limiting step in ribosome biogenesis, which is essential for cell survival. Despite its global function, disruptions in ribosome biogenesis cause tissue-specific birth defects called ribosomopathies, which frequently affect craniofacial development. Here, we describe a cellular and molecular mechanism underlying the susceptibility of craniofacial development to disruptions in Pol I transcription. We show that Pol I subunits are highly expressed in the neuroepithelium and neural crest cells (NCC), which generate most of the craniofacial skeleton. High expression of Pol I subunits sustains elevated rRNA transcription in NCC progenitors, which supports their high tissue-specific levels of protein translation, but also makes NCC particularly sensitive to rRNA synthesis defects. Consistent with this model, NCC-specific deletion of Pol I subunits Polr1a, Polr1c, and associated factor Tcof1 in mice cell-autonomously diminishes rRNA synthesis, which causes an imbalance between rRNA and ribosomal proteins. This leads to increased binding of ribosomal proteins Rpl5 and Rpl11 to Mdm2 and concomitantly diminished binding between Mdm2 and p53. Consequently, p53 protein accumulates, resulting in NCC apoptosis and craniofacial anomalies. Furthermore, compound mutations in Pol I subunits and associated factors specifically exacerbates the craniofacial anomalies characteristic of the ribosomopathies Treacher Collins Syndrome and Acrofacial Dysostosis-Cincinnati Type. Altogether, our novel results demonstrate a dynamic spatiotemporal requirement for rRNA transcription during mammalian cranial NCC development and corresponding tissue-specific threshold sensitivities to disruptions in rRNA transcription in the pathogenesis of congenital craniofacial disorders. Significance statementRNA Polymerase I (Pol I) mediated rRNA transcription is required for protein synthesis in all tissues for normal growth and survival as well as for proper embryonic development. Interestingly, disruptions in Pol I mediated transcription perturb ribosome biogenesis and lead to tissue-specific birth defects, which commonly affect the head and face. Our novel results show that during mouse development, Pol I mediated rRNA transcription and protein translation is tissue-specifically elevated in neural crest cells, which give rise to bone, cartilage, and ganglia of the head and face. Using new mouse models, we further show that neural crest cells are highly sensitive to disruptions in Pol I and that when rRNA synthesis is genetically downregulated, it specifically results in craniofacial anomalies.

developmental biology↗