Loss of Sbds in Shwachman-Diamond Syndrome Murine Model Leads to Reduction of 80S Ribosomes and Altered Transcript Binding
Year: 2016
Type: dissertation
Abstract: Shwachman-Diamond syndrome (SDS) is an autosomal recessive disease characterized by growth retardation, exocrine pancreatic dysfunction, skeletal dysplasia, cognitive impairment and bone marrow failure. SDS is caused by mutations in SBDS (Shwachman-Bodian-Diamond syndrome). A recent model proposes that SBDS/Sbds functions together with EFL1/Efl1 to release EIF6/Eif6 from the pre-60S complex, enabling ribosomal subunit joining for translation initiation. To assess the protein synthesis deficiency that has been detected in SDS, I examined ribosomal profiles of murine fetal organs with the SDS-associated missense mutation, R126T (SbdsR126T/R126T). The SDS organ extracts revealed reduced 80S monosomes and preserved polysomes, with no ribosomal subunit imbalance compared to matched controls. Further, Eif6 was found to bind to both the 60S and 80S ribosome complexes in mutants in contrast to only 60S complexes in controls. To investigate these changes and to learn how the SDS translatome is affected, total and polysomal mRNAs of mutant and control samples were studied using cDNA microarray analyses. By comparing individual polysomal transcripts to respective total transcript levels, I found 799 transcripts (of 18,936 analyzed) with altered polysome loading in mutant fetal livers, with 634 being increased. Changes in polysome loading did not correspond with steady state protein levels, as indicated by proteome analysis using label-free mass spectrometry. Rather, these changes correlated with physical features of the transcripts, including 5' untranslated region composition as well as the lengths and nucleotide contents of the open reading frame and the 3' untranslated regions. Together, I conclude that the untimely release of Eif6 due to Sbds deficiency results in ribosomes with compromised translation initiation and that SDS disease phenotypes reflect protein synthesis insufficiency and the formation of sub-populations of â SDS ribosomesâ with non- or poor- translating capability.
Source: TSpace (University of Toronto)
Author: Hongrui Liu
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: green
OpenAlex ID: W2735111232