All ETDs from UAB

Advisory Committee Chair

Ching-Yi Chen

Advisory Committee Members

David M Bedwell

Jacqueline N Parker

Thomas M Ryan

Tim M Townes

Document Type

Dissertation

Date of Award

2011

Degree Name by School

Doctor of Philosophy (PhD) Heersink School of Medicine

Abstract

Several strategies are used in eukaryotic cells in order to determine the gene expression level, including the transcriptional and post-transcriptional mechanisms. One of the post-transcriptional mechanisms is the regulation of mRNA stability, which varies considerably from one mRNA species to another. Previous studies have shown that inherently unstable mRNAs encoding cytokines and proto-oncogenes contain the AU-rich elements (AREs) in the 3' untranslated regions (UTRs). Their decay requires decay-promoting RNA-binding proteins that recognize the AREs and recruit mRNA decay machineries to facilitate the rapid decay of targeting mRNA. KH-type splicing regulatory protein (KSRP) was previously identified as an ARE decay promoting factor. Although several cytokine genes have been reported as KSRP targets, to date there is still a lack of evidence of the physiological roles played by KSRP, and its in vivo mRNA targets are still unknown. In this study, we have generated a null KSRP knockout mouse model and identified type I interferon (IFN-α and IFN-ß) as the direct targets of KSRP. Known by its transient accumulation upon viral infection, the ARE-containing type I IFN is rapidly shut off thereafter upon its induction, partly mediated through the mechanism of post-transcriptional regulation. We showed that KSRP knockout mouse embryonic fibroblasts (MEFs) produce higher levels of Ifna and Ifnb mRNAs in response to viral infection as a result of decreased mRNA decay. Consequently, the increased type I IFN expression in both mRNA and protein levels, likely caused by its altered mRNA decay, rendered Ksrp-/- cells and mice refractory to both DNA and RNA virus infection. Reporter mRNA decay analysis further showed that KSRP is required for the decay of Ifna4 and Ifnb mRNAs by directly interacting with their 3' UTRs. Our findings support a role of post-transcriptional mechanism in the control of type I IFN gene expression and highlight the function of KSRP in innate immunity by negatively regulating type I IFN production via rapid mRNA decay.

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