Post-transcriptional Regulation of Hes7 via Alternative Polyadenylation of the 3’UTR
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Date
2016-05
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The Ohio State University
Abstract
During vertebrate embryonic development, the axial skeleton forms from transient structures called somites during the process of somitogenesis. This process is regulated by a segmentation clock which allows embryos to integrate temporal and positional information through synchronized pulses of gene expression. The period of the clock changes across the presomitic mesoderm (PSM) such that the cells in the anterior PSM experiences slower oscillations than those in the posterior PSM. Currently, the mechanism by which the clock period changes across the PSM is unclear. Additionally, the clock period varies between species but is consistent within a species. Many models suggest that the oscillation rate of the clock in mice is set by the period of Hes7 oscillations. If the speed of Hes7 oscillations determines the period of the clock, then mechanisms that regulate Hes7 transcript turnover may be important for normal clock function and may influence the clock period. This is because the rate of transcript turnover, determined by transcript half-life, affects the amount of time that lapses between turning off transcription and turning off gene activity by degrading all mRNA and protein. Regulation of transcript stability and turnover is often controlled by the 3' untranslated region (3'UTR). In Hes7, there are three 3'UTR isoforms of different lengths produced through alternative polyadenylation. This means that the use of alternative polyadenylation sites may influence Hes7 turnover in the PSM and contribute to the change in clock frequency across the PSM or between species. To test whether the different Hes7 3'UTR isoforms could impact RNA turnover, the Hes7 3'UTRs have been mutated to force the expression of a single isoform. These forced-polyadenylation UTRs were tested to analyze their impact on transcript stability through Luciferase assays. We find that the Hes7 3'UTR is associated with decreased protein production compared to controls and that transcripts containing the longer 3'UTR isoforms produce significantly less protein than the short isoforms. Further research will determine whether the functional differences between 3'UTR isoforms arise due to changes in transcript turnover or changes in translational efficiency and will examine mechanisms regulating these effects.
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Keywords
Somitogenesis, Hes7, Alternative polyadenylation, 3'UTR