Poster abstracts
Poster number 73 submitted by Lucia Johnson
Translational control of a unique bicistronic gene linked to Prader-Willi Syndrome
Lucia Johnson (Biological Sciences Department, Carnegie Mellon University), Gemma May (Biological Sciences Department, Carnegie Mellon University), Robert Nicholls (Pediatrics Department, UPMC), Joel McManus (Biological Sciences Department, Carnegie Mellon University)
Abstract:
Prader-Willi Syndrome (PWS) is a developmental disorder characterized by low-muscle tone, developmental delays, intellectual impairment, and hyperphagia (1). Diagnosis is determined by detection of genomic abnormalities in chromosome 15 (15q11.2-q13), including deletions or epigenetic errors in the paternal chromosome, or inheritance of two maternal copies and no paternal copy of the chromosome (maternal parental disomy; 2). Within this region lies a unique bicistronic gene, SNURF-SNRPN, that encodes the SNURF (SNRPN Upstream Reading Frame) and SNRPN (Small Nuclear Riboprotein N) genes (3). SNRPN encodes SmN, a neuronal-specific spliceosomal snRNP protein, but the function of SNURF remains to be determined (1). Because eukaryotic translation typically initiates via directional scanning, SNURF’s presence should prevent translation of SNRPN. How, then, is SNRPN translated? To investigate this, we transfected tissue culture cells with luciferase reporter mRNAs. Our results show that translation of SNRPN requires cap-dependent directional scanning, indicating SNRPN does not have an Internal Ribosome Entry Site. Intriguingly, we found a highly conserved upstream open reading frame (uORF) upstream of SNURF that promotes SNRPN translation. Mutation of the uORF start codon decreases translation initiation at SNRPN in a SNURF-dependent manner. These results suggest that a uORF, not an IRES, is responsible for efficient translation of SNURF-SNRPN, likely due to delayed reinitiation. We are carrying out additional experiments to further test this model and evaluate the potential for translational regulation under stress in a variety of PWS relevant cell types.
References:
1. Chung, Michael S et al. “Prader-Willi syndrome: reflections on seminal studies and future therapies.” Open biology vol. 10,9 (2020): 200195. doi:10.1098/rsob.200195
2. Driscoll DJ, Miller JL, Cassidy SB. Prader-Willi Syndrome. 1998 Oct 6 [Updated 2023 Nov 2]. In: Adam MP, Feldman J, Mirzaa GM, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2024. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1330/#
3. Gray, T A et al. “An imprinted, mammalian bicistronic transcript encodes two independent proteins.” Proceedings of the National Academy of Sciences of the United States of America vol. 96,10 (1999): 5616-21. doi:10.1073/pnas.96.10.561
Keywords: translation