Escherichia coli ribosomal protein S1 enhances the kinetics of ribosome biogenesis and RNA decay

Escherichia coli ribosomal protein S1 is essential for translation initiation of mRNAs and for cellular viability. Two oligonucleotide binding (OB)-fold domains located in the C-terminus of S1 are dispensable for growth, but their deletion causes a cold-shock phenotype, loss of motility and deregulation of RNA mediated stress responses. Surprisingly, the expression of the small regulatory RNA RyhB and one of its repressed target mRNA, sodB, are enhanced in the mutant strain lacking the two OB domains. Using in vivo and in vitro approaches, we show that RyhB retains its capacity to repress translation of target mRNAs in the mutant strain but becomes deficient in triggering rapid turnover of those transcripts. In addition, the mutant is defective in of the final step of the RNase E-dependent maturation of the 16S rRNA. This work unveils an unexpected function of S1 in facilitating ribosome biogenesis and RyhB-dependent mRNA decay mediated by the RNA degradosome. Through its RNA chaperone activity, S1 participates to the coupling between ribosome biogenesis, translation, and RNA decay.

Ribosomal protein S1 plays a critical role in horizontal gene transfer by mediating the expression of foreign mRNAs

The emergence of multi-antibiotic resistant bacteria is one of the largest threats to global heath. This rise is due to the genomic plasticity of bacteria, allowing rapid acquisition of antibiotic resistance through the uptake of foreign DNA (i.e. horizontal gene transfer, HGT). This genomic plasticity is not limited to DNA from bacteria, highly divergent (trans-kingdom) mRNA have been reported to drive translation in E. coli. Trans-kingdom activity has been attributed to mRNA tertiary structure suggesting the bacterial translation machinery bottle-necks HGT, restricting the expression of foreign DNA. However, here we show that tertiary structure is not responsible for ribosome recruitment and that the translation efficiency is dependent on ribosomal protein S1 and an A-rich Shine-Dalgarno-like element. The S1-facilitated ability of ribosomes to identify and exploit A-rich sequences in foreign RNA highlights the important role that S1 plays in horizontal gene transfer, the robustness of canonical prokaryotic translation, and bacterial evolution.

Albino seedling lethality 4; Chloroplast 30S Ribosomal Protein S1 is Required for Chloroplast Ribosome Biogenesis and Early Chloroplast Development in Rice

Background Ribosomes responsible for transcription and translation of plastid-encoded proteins in chloroplasts are essential for chloroplast development and plant growth. Although most ribosomal proteins in plastids have been identified, the molecular mechanisms regulating chloroplast biogenesis remain to be investigated. Results Here, we identified albinic seedling mutant albino seedling lethality 4 (asl4) caused by disruption of 30S ribosomal protein S1 that is targeted to the chloroplast. The mutant was defective in early chloroplast development and chlorophyll (Chl) biosynthesis. A 2855-bp deletion in the ASL4 allele was verified as responsible for the mutant phenotype by complementation tests. Expression analysis revealed that the ASL4 allele was highly expressed in leaf 4 sections and newly expanded leaves during early leaf development. Expression levels were increased by exposure to light following darkness. Some genes involved in chloroplast biogenesis were up-regulated and others down-regulated in asl4 mutant tissues compared to wild type. Plastid-encoded plastid RNA polymerase (PEP)-dependent photosynthesis genes and nuclear-encoded phage-type RNA polymerase (NEP)-dependent housekeeping genes were separately down-regulated and up-regulated, suggesting that plastid transcription was impaired in the mutant. Transcriptome and western blot analyses showed that levels of most plastid-encoded genes and proteins were reduced in the mutant. The decreased contents of chloroplast rRNAs and ribosomal proteins indicated that chloroplast ribosome biogenesis was impaired in the asl4 mutant. Conclusions Rice ASL4 encodes 30S ribosomal protein S1, which is targeted to the chloroplast. ASL4 is essential for chloroplast ribosome biogenesis and early chloroplast development. These data will facilitate efforts to further elucidate the molecular mechanism of chloroplast biogenesis.

Albino seedling lethality 4 ; chloroplast 30S ribosomal protein S1 required for chloroplast ribosome biogenesis and early chloroplast development in rice

Background : Ribosomes responsible for transcription and translation of plastid-encoded proteins in chloroplasts are essential for chloroplast development and plant growth. Although most ribosomal proteins in plastids have been identified, the molecular mechanisms regulating chloroplast biogenesis remain to be investigated. Results: Here, we identified albinic seedling mutant asl4 caused by disruption of 30S ribosomal protein S1 that is targeted to the chloroplast . The mutant was defective in early chloroplast development and chlorophyll biosynthesis . A 2,855-bp deletion in the ASL4 allele was verified as responsible for the mutant phenotype by complementation tests. Expression analysis revealed that the ASL4 allele was highly expressed in leaf 4 sections and newly expanded leaves during early leaf development. Expression levels were increased by exposure to light following darkness. Some genes involved in chloroplast biogenesis were up-regulated and others down-regulated in asl4 mutant tissues compared to wild type. PEP-dependent photosynthesis genes and NEP-dependent housekeeping genes were separately down-regulated and up-regulated, suggesting that plastid transcription was impaired in the mutant. Transcriptome and western blot analyses showed that levels of most plastid-encoded genes and proteins were reduced in the mutant. The decreased contents of chloroplast rRNAs and ribosomal proteins indicated that chloroplast ribosome biogenesis was impaired in the asl4 mutant. Conclusion: Rice ASL4 encodes 30S ribosomal protein S1, which is targeted to the chloroplast. ASL4 is essential for chloroplast ribosome biogenesis and early chloroplast development. These data will facilitate efforts to further elucidate the molecular mechanism of chloroplast biogenesis.

Computational Insight into the Binding Mechanism of Pyrazinoic Acid to RpsA Protein

Background: Resistance to the critical first line anti-tubercular drug, Pyrazinamide, is a significant obstacle to achieving the global end to tuberculosis targets. Approximately 50% of multidrug-resistant tuberculosis and over 90% of extensively drug-resistant tuberculosis strains are also Pyrazinamide resistant. Pyrazinamide is a pro-drug that reduce the duration of tuberculosis therapy time by 9-12 months, while used as an anti-biotic in the 1st- & 2nd-line tuberculosis treatment regimens. Pyrazinamidase is an enzyme, encoded by pncA gene, is responsible for the amide hydrolysis of Pyrazinamide into active Pyrazinoic acid. Pyrazinoic acid, could inhibit trans-translation by binding to Ribosomal protein S1 and competing with tmRNA, the natural cofactor of Ribosomal protein S1. Although pncA mutations have been commonly associated with Pyrazinamide resistance, a small number of resistance cases have been associated with mutations in Ribosomal protein S1. Ribosomal protein S1was recently identified as a possible target of Pyrazinamide based on its binding activity to Pyrazinoic acid and the capacity to inhibit trans-translation. Objective: Despite the critical role played by Pyrazinamide, its mechanisms of action are not yet fully understood. Therefore, an effort to explore the resistance mechanism toward Pyrazinamide drug in Mycobacterium (M.) tuberculosis. Methods: An extensive molecular dynamics simulation was performed using the AMBER software package. We mutated residues of the binding site (i.e., F307A, F310A, and R357A) in the RpsA S1 domain to address the drug-resistant mechanism of RpsA in complex that might be responsible for Pyrazinamide resistance. Moreover, it is challenging to collect the drug mutant combine complex of a protein by single-crystal X-ray diffraction. Thus, the total three structures were prepared by inducing mutations in the wild-type protein using PyMol. Results: The dynamics results revealed that mutation in binding pocket produced Pyrazinamide resistance due to the specificity of these residues in binding pockets which result in scarcity of hydrophobic and hydrogen bonding interaction with Pyrazinoic acid, which increases the CA-distance between the binding pocket residues as compared to wild type RpsA that lead to structural instability. Conclusion: The overall dynamic results will provide useful information behind the drug resistance mechanism to manage tuberculosis and also helps in better management for future drug resistance.