Abstract PR02: The diverse roles of long noncoding RNAs in the p53 tumor suppressor pathway

The p53 tumor suppressor is a transcription factor, which plays a central role in the cellular response to DNA damage and oncogenic stress. Using genetic approaches in the mouse as well as antisense technology, we have previously shown that the p53-regulated lncRNA, lincRNA-p21 activates the expression of its neighboring gene, the critical G1/S checkpoint mediator, p21. Mechanistically, we found that lincRNA-p21 localizes at its site of transcription, where it acts in cis to stabilize the binding of p53 and its transcriptional co-activator hnRNP-K at the promoter of p21. Importantly, using CRISPR-based approaches to modify the endogenous lincRNA-p21 locus in primary human fibroblasts, we show that the role of lincRNA-p21 in promoting p21 levels is conserved between mouse and human. To expand our understanding of the contribution of lncRNAs to the p53 tumor suppressor pathway, we have performed p53 ChIPseq and RNAseq under conditions of oncogenic stress and identified multiple previously uncharacterized lncRNAs that are regulated in a p53-dependent manner. One of them, lincRNA-Dhx15 is a novel lncRNA expressed from a bidirectional promoter shared with the RNA helicase Dhx15. LincRNA-Dhx15 is a direct target of p53 by virtue of multiple p53 response elements located in its first intron and appears to be preferentially expressed under conditions of senescence. We have generated a conditional knockout of lincRNA-Dhx15 in the mouse and found that absence of lincRNA-Dhx15 leads to impaired induction of senescence following prolonged exposure to DNA damage. Moreover, by gene expression profiling, we observed a downregulation of a subset of p53 target genes, suggesting that lincRNA-Dhx15 plays a global role in the p53 pathway. Surprisingly, we found that lincRNA-Dhx15 is exported to the cytoplasm and appears to promote the translational of p53 itself. The mechanistic basis for lincRNA-Dhx15 function is under active investigation. Altogether, these studies reveal that p53-regulated lncRNAs act through diverse mechanisms to add important layers of regulation to the p53 transcriptional network. Citation Format: Jordan Bendor, Jesse Zamudio, Tyler Jacks, Nadva Dimitrova. The diverse roles of long noncoding RNAs in the p53 tumor suppressor pathway. [abstract]. In: Proceedings of the AACR Special Conference on Noncoding RNAs and Cancer: Mechanisms to Medicines ; 2015 Dec 4-7; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2016;76(6 Suppl):Abstract nr PR02.