Poster abstracts
Poster number 36 submitted by Fawwaz Naeem
The main purpose of the anti-Shine-Dalgarno sequence of 16S rRNA in Flavobacterium johnsoniae is to enable translation of the bS21 gene
Fawwaz Naeem (OSBP, The Ohio State University. Center for RNA Biology, The Ohio State University), Zakkary A. McNutt (OSBP, The Ohio State University. Center for RNA Biology, The Ohio State University), Kurt Fredrick (Department of Microbiology, The Ohio State University)
Abstract:
In many bacteria, initiation of translation typically involves base pairing between the Shine-Dalgarno (SD) sequence of mRNA and the anti-SD (ASD) of 16S rRNA. However, bioinformatics studies have revealed that certain groups of bacteria, including the Bacteroidia, lack SD sequences in mRNA. Bacteroidia ribosomes contain the ASD but fail to recognize SD sequences, both in vivo and in vitro. A cryo-EM structure of the Flavobacterium johnsoniae ribosome shows that the 3’ tail of 16S rRNA is sequestered in a pocket formed by bS21, bS18, and bS6 on the 30S platform, explaining the structural basis of ASD inhibition. Interestingly, one gene in F. johnsoniae contains a strong SD sequence—rpsU, which encodes bS21. F. johnsoniae ribosomes lacking bS21 exhibit a liberated ASD and translate rpsU at a higher rate, which creates a feedback loop that autoregulates bS21 production. In this work, we systematically target the ASD of each 16S rRNA gene in F. johnsoniae, substituting the core element at 4 of 5 positions (CCUCC to GAAGC). Sequential allelic replacements have little effect on cell growth until the last gene is changed. The final strain, in which all the ribosomes in the cell contain a mutant ASD sequence, grows very slowly, with a doubling time 4 folds larger than wild-type. Remarkably, this growth phenotype can be rescued (almost fully) by a plasmid carrying rpsU with an alternative (SD-less) translation initiation region. These data show that the main function of the ASD involves translation of rpsU in F. johnsoniae.
References:
Jha, Vikash, Bappaditya Roy, Dushyant Jahagirdar, Zakkary A McNutt, Elan A Shatoff, Bethany L Boleratz, Dean E Watkins, et al. 2021. “Structural Basis of Sequestration of the Anti-Shine-Dalgarno Sequence in the Bacteroidetes Ribosome.” Nucleic Acids Research. 49 (1): 547–67. https://doi.org/10.1093/nar/gkaa1195
McNutt, Zakkary A, Bappaditya Roy, Bryan T Gemler, Elan A Shatoff, Kyung-Mee Moon, Leonard J Foster, Ralf Bundschuh, and Kurt Fredrick. 2023. “Ribosomes Lacking bS21 Gain Function to Regulate Protein Synthesis in Flavobacterium Johnsoniae.” Nucleic Acids Research. 51 (4): 1927–1942. https://doi.org/10.1093/nar/gkad047.
Keywords: Ribosome, 16S rRNA , ribosomal protein bS21