Alternative splicing of RNA transcripts is emerging as a major mechanism for expanding the proteome. Splice pattern changes are found in numerous diseases and cancers, indicating the importance of tight control over this process. While the mechanism of splicing has been described in detail, it is less clear how a cell is able to modify its splicing patterns in response to different conditions. Our lab previously demonstrated that DNA damage can induce SFRS6, the gene coding for splicing factor SRp55, thereby leading to changes in the splicing patterns of several target genes related to survival and apoptosis. We also showed that this induction can be inhibited by p53. In this study we investigated the mechanism by which p53 inhibits SFRS6 transcription. Utilizing a luciferase reporter plasmid, we found that two putative p53 REs in the SFRS6 promoter were critical for this inhibition. ChIP and EMSA were then employed to confirm that p53 activated by DNA damage binds directly to these REs on the SFRS6 promoter. Because SFRS6 is modulated by p53 in response to DNA damage, we investigated the downstream effects of this splice factor. SFRS6 regulates the splicing of many genes related to DNA damage and apoptosis, one of which is IL-24. Silencing of SFRS6 results in an increase in a splice variant that lacks exons 2 and 3, while overexpression results in an overall shift away from the larger splice isoforms. In examining the splicing of IL-24, we identified numerous splice variants that have not been previously reported. We characterized these isoforms and have now described five novel splice variants of this important tumor suppressor. We examined the function of these novel variants and found that several of them induce apoptosis in tumor cells with different efficacies, while one of them does not. The results of this study provide further insight into functional splicing regulation as it is controlled by upstream events. Understanding the control of splicing has the potential to provide novel clinical insights into the ways that disordered splicing plays a role in disease. In particular, the novel isoforms of the tumor suppressor IL-24 suggest additional options for the treatment of various cancers.
Microbiology and Molecular Genetics
Microbiology, Molecular Biology and Biochemistry
School of Medicine
Daisy De Leon
Doctor of Philosophy (PhD)
Year Degree Awarded
Date (Title Page)
Library of Congress/MESH Subject Headings
Alternative Splicing -- genetics; Spliceosomes; Interleukin-24; Tumor Suppressor Protein p53; Cell Line, Tumor; Apoptosis Regulatory Proteins; serine-argine-rich splicing proteins [Supplementary Concept]; Gene Expression Regulation.
Loma Linda University Libraries
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Schmidt, Erin L., "Splice Factor SFRS6: Regulation by p53 and Effect on IL-24 Splicing" (2010). Loma Linda University Electronic Theses, Dissertations & Projects. 771.
Loma Linda University Electronic Theses and Dissertations
Loma Linda University. Del E. Webb Memorial Library. University Archives