Poster abstracts

Poster number 1 submitted by Yehong Qiu

A cancer-associated mutation in a human mitochondrial tRNA induces structural rearrangement

Yehong Qiu (Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University), Edric K. Choi (Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University), Venkat Gopalan (Department of Chemistry and Biochemistry and Center for RNA Biology, The Ohio State University)

Abstract:
Human mitochondrial (hmt) tRNA genes comprise only 10% of the hmt genome, yet nearly half the mitochondrial disease-associated mutations reside in these genes1. With these mutations, there is no safety net in the form of genetic redundancy as the hmt genome has only one locus each for the 22 hmt-tRNAs. In mitochondria, transcription generates long polycistronic RNAs, with tRNAs serving as “punctuation” points to facilitate accurate biogenesis of all RNAs. Thus, mutations in tRNA genes adversely affect not only translation but other mitochondrial processes. However, the molecular basis for various diseases arising from mt tRNA mutations is unclear. Here, we sought to test the hypothesis that mt-tRNAs toggle between native and non-native conformations, and that a hepatocellular carcinoma-associated mutation (C6U) in hmt tRNAAla might selectively stabilize a non-native fold and thereby prevent 5′-processing by hmt-RNase P. Thermal denaturation studies revealed unexpectedly that the mutant has a higher melting temperature (Tm) compared to the wild-type, a finding that we attribute to stabilization of a non-native conformation. Additional mutations that were engineered to either stabilize or destabilize the non-native fold behaved as predicted. Results from ongoing selective 2′-hydroxyl acylation analyzed by primer extension (SHAPE) experiments are expected to further refine our structural models for the native and non-native folds for hmt tRNAAla. Taken together, our studies provide a glimpse into a potential mechanism for mitochondrial disease pathogenesis: impaired biogenesis caused by hmt tRNA mutations, which unduly bias an intrinsic conformational switch.

References:
1 Schon EA, DiMauro S, and Hirano M. (2012) Human mitochondrial DNA: roles of inherited and somatic mutations. Nature Rev Genet., 13: 878-890.

Keywords: mitochondrial tRNA, thermal denaturation, SHAPE