Long noncoding RNA structural domains essential for regulation of gene expression

Abstract

Recent studies have shown that long noncoding RNAs (lncRNAs) play roles in a broad range of cellular processes. I choose two lncRNAs which are relevant cancers to investigate correlation between their structure and function. First, brain cytoplasmic RNA (BC200) acts as a translational modulator of local protein synthesis at dendrites. Herein I demonstrated minimum regions and enhancing regions of activation and inhibition for translation efficiency in BC200 RNA. Especially, these enhancing regions in Alu domain must be required in cap-dependent translation. These results demonstrate the importance of Alu domain in translation inhibition. Next, I identified hnRNP E1 and hnRNP E2 as BC200 RNA-interacting proteins by Y3H. I found that: these hnRNA proteins could restore BC200 RNA-inhibited translation

BC200 RNA interacts with hnRNP E1 and E2 mainly through its unique 3’ C-rich domain

and the RNA binding specificities and modes of the two proteins differed somewhat. These results offer new insights into the regulation of BC200 RNA-mediated translation inhibition. Second, the steroid receptor RNA activator (SRA) acts as a putative coactivator for steroid receptor-mediated transcription. Here, I first examined the effects of each domain on the coactivation of estrogen receptor $\alpha$ ($ER \alpha$)-mediated transcription. Domain deletion analysis using a luciferase reporter gene in HeLa cells showed that the deletion of any domain decreased the luciferase activity, and that deletion of domain III caused the largest decrease. This domain III deletion effect was not recovered by co-expression of domain III alone

moreover, the expression of domain III fragments inhibited luciferase expression in HeLa cells. Moreover, a fragment containing helices H15-H18 reduced $ER \alpha$ -responsive gene expression in MCF-7 breast cancer cells, suggesting that these conserved helices are important to the SRA RNA-mediated regulation of $ER \alpha$ -mediated transcription. In summary, this thesis proposed closed association between RNA structure and function using BC200 RNA and SRA RNA.