Poster abstracts

Poster number 154 submitted by Alice Youle

Translational output of CFTR is regulated by multiple elements in 5’UTR

Alice M. Youle (Biological Chemistry, University of Michigan), Rachel O. Niederer (Biological Chemistry, University of Michigan)

Abstract:
Cystic fibrosis is a monogenic disorder primarily caused by mutations to the chloride ion channel protein CFTR. Over 2000 causative genomic variants have been identified, which result in a wide range of molecular phenotypes, including low expression of CFTR, or expression of CFTR with reduced or abolished function1. The amount of functional CFTR is tightly connected to the severity of disease, which has focused therapeutic efforts on increasing expression of functional CFTR. The 5’ untranslated region (UTR) of an RNA is an important feature in regulating translation of an RNA into protein. CFTR has several elements in its 5’UTR which are commonly inhibitory for translation, including secondary structure and an upstream start codon (uAUG). However, the interplay of these regulatory elements within 5’UTR, and their combined impact on translational output requires further characterization. We identified that secondary structure within the 5’UTR suppresses translation of CFTR in vitro particularly when located at the 5’end of the mRNA, and that shifting the structure downstream by only 4 nucleotides is sufficient to promote translation. This is consistent with previous work suggesting the highly structured 5’ end of CFTR RNA inhibits translation initiation2. Surprisingly, we also find that the uAUG is not inhibitory for translation of CFTR as expected, but rather enhances translational output. We propose that the uAUG may enhance translation by promoting translational re-initiation. These findings establish the CFTR 5’UTR as an interesting model for uncovering mechanistic details of RNA translation regulation, as well as a potential therapeutic target to increase CFTR expression in CF patients.

References:
1) Cystic Fibrosis Mutation Database (2011). Available online at: http://www.genet.sickkids.on.ca
2) Sasaki, S., Sun, R., Bui, H.-H., Crosby, J. R., Monia, B. P., & Guo, S. (2019). Steric Inhibition of 5’ UTR Regulatory Elements Results in Upregulation of Human CFTR. Molecular Therapy: The Journal of the American Society of Gene Therapy, 27(10), 1749–1757. https://doi.org/10.1016/j.ymthe.2019.06.016

Keywords: 5UTR, secondary structure, translation reinitiation