Poster abstracts
Poster number 10 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, The Ohio State University. Department of Microbiology, The Ohio State University. Center for RNA biology, The Ohio State University), Kurt Fredrick (Ohio state Biochemistry program, The Ohio State University. Department of Microbiology, The Ohio State University. 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. Translational GTPases, 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 SRL remains unclear. A study from the Noller group 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 exhibit a major assembly defect. In particular, block 4 of the 50S subunit, which includes the components of the peptidyl transferase center, fails to fold. We hypothesize that this assembly defect results from disruption of interactions with one or more translational GTPases rather than an intrinsic rRNA folding problem. During the assembly of large subunit, SRL folds early on as part of block 1. We envision that GTPases could then transiently bind via the SRL and facilitate subsequent folding events. Here, we describe in vitro 50S subunit reconstitution experiments to investigate this 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: Sarcin-ricin loop, Ribosome assembly, Translational GTPases