Poster abstracts
Poster number 21 submitted by Sepideh Fakhretaha Aval
Role of the sarcin-ricin loop (SRL) of 23S rRNA in assembly of the 50S ribosomal subunit
Sepideh Fakhretaha Aval (Ohio state Biochemistry program, Department of Microbiology, Center for RNA biology, The Ohio State University), Kurt Fredrick (Ohio state Biochemistry program, Department of Microbiology, Center for RNA biology, The Ohio State University)
Abstract:
The sarcin-ricin loop (SRL) is one of the most conserved segments of the large subunit ribosomal RNA (rRNA). Translational GTPases (trGTPases), such as EF-G and EF-Tu and IF2, interact with the SRL, and this interaction is essential for GTP hydrolysis. Cleavage and modification of the SRL by cytotoxins α-sarcin and ricin disrupt GTPase-ribosome interaction, leading to reduced protein synthesis and cell death. However, the full role of the of SRL remains unclear. A previous study showed that expression of 23S rRNA lacking the SRL confers a dominant lethal phenotype in E. coli. These ΔSRL ribosomes were purified from cells and found to be completely inactive in protein synthesis. Surprisingly, further analysis showed that ΔSRL ribosomes are not fully assembled. In particular, block 4 of the 50S subunit, which includes the components of the peptidyl transferase center, fails to fold. This defect could be due to loss of interactions between SRL and either (i) rRNA and/or ribosomal proteins or (ii) other (non-ribosomal) factors in the cell, such as trGTPases. Here, we describe in vitro 50S subunit reconstitution experiments and analysis of resulting particles. Our initial findings suggest that the defect is specific to ribosome biogenesis in the cell, consistent with the latter hypothesis.
References:
Moazed D, Robertson JM, Noller HF. Interaction of elongation factors EF-G and EF-Tu with a conserved loop in 23S RNA. Nature. 1988;334(6180):362-364. doi:10.1038/334362a0
García-Ortega L, Alvarez-García E, Gavilanes JG, Martínez-del-Pozo A, Joseph S. Cleavage of the sarcin-ricin loop of 23S rRNA differentially affects EF-G and EF-Tu binding. Nucleic Acids Res. 2010;38(12):4108-4119. doi:10.1093/nar/gkq151
Lancaster L, Lambert NJ, Maklan EJ, Horan LH, Noller HF. The sarcin-ricin loop of 23S rRNA is essential for assembly of the functional core of the 50S ribosomal subunit. RNA. 2008;14(10):1999-2012. doi:10.1261/rna.1202108
Davis JH, Williamson JR. Structure and dynamics of bacterial ribosome biogenesis. Philos Trans R Soc Lond B Biol Sci. 2017;372(1716):20160181. doi:10.1098/rstb.2016.0181
Keywords: Ribosome biogenesis, Sarcin-ricin loop, 23S rRNA