Post-transcriptional regulation of DNA Damage Binding protein 2 and the identification of a novel mRNA stability determinant

Title: Post-transcriptional regulation of DNA Damage Binding protein 2 and the identification of a novel mRNA stability determinant
Authors: Melanson, Brian D
Date: 2010
Abstract: UV light is a potent inducer of the p53 tumour suppressor, a transcription factor that positively regulates a large number of UV-responsive transcripts. However, UV light also induces RNA polymerase-blocking DNA lesions in a stochastic manner. This poses a challenge to the coordinated regulation of UV-responsive gene expression. We previously reported a UV dose-dependent shift in the spectrum ofp53 induced target genes towards smaller genes with fewer and smaller introns. Here, we report that the DDB2 transcript is induced more strongly than other similar sized p53 target genes (FAS or MDM2) following UV exposure. The preferential induction ofDDB2 mRNA is not due to the expression of a cryptic internal promoter. Instead, the DDB2 transcript was found to be unstable prior to UV exposure and its half-life was increased significantly in a UV dose-dependent manner. UV light did not affect the stability of the FAS or MDM2 mRNAs. Cis-acting elements within the 3'UTR of transiently expressed transcripts often target labile mRNAs for rapid degradation. The DDB2 3'UTR induced a rapid increase in mRNA turnover of an EGFP reporter gene that was also observed at the protein level. Using this reporter system, we localized a destabilizing element within a 49 nucleotide region, and have termed this the 3'UTR DDB2 destabilizing element (3 'DDE). Structural analysis of the 3'DDE predicted the presence of distinct structural features. Mutational analysis of these structures further isolated a minimal 14nt region that is required to elicit rapid mRNA turnover. Given the role ofDDB2 in nucleotide excision repair, we suggest that its post-transcriptional regulation contributes to recovery from UV-induced DNA damage. In addition to DDB2, we found that the mRNA ofp53 target-genes are generally short-lived. We propose that this phenomenon has evolved as a method to keep p53-mediated pro-apoptotic and anti-survival stress responses in check.
CollectionTh├Ęses, 1910 - 2010 // Theses, 1910 - 2010
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