Abstract 514: Lncrna uca1 interacts directly with angiomotin to activate Hippo-YAP signaling in epithelial ovarian cancer

Abstract

Abstract The long noncoding RNA (lncRNA) urothelial cancer associated 1 (UCA1) is upregulated in multiple cancers, including epithelial ovarian cancer (EOC). Our present study aims to dissect the functional and mechanistic role of UCA1 in EOC. We first explored the effects of stable UCA1 knockout mediated by CRISPR/Cas9 genome editing. The effects of UCA1 loss were more profound in vivo, as UCA1 knockout significantly impaired tumor growth in a mouse xenograft model. Pathways downstream of UCA1 were catalogued using reverse phase protein arrays, which revealed that YAP signaling is activated in UCA1-overexpressing ovarian cancer cells. To characterize the UCA1 interactome, in vivo RNA antisense purification (UCA1-iRAP) experiments were performed using a modified ChIRP and RAP protocol to isolate in vivo RNA direct interactomes based on hybridization of short (20 base) biotinylated probes at a physiologically relevant temperature (37°C). UCA1-iRAP was performed using an EOC cell model, and proteins extracted were profiled by mass spectrometry (MS). Altogether, 19 unique proteins were reproducibly detected by UCA1-iRAP-MS. Interestingly 16 of these UCA1-associated proteins were not previously known RNA-binding proteins. Integration of UCA1-iRAP-MS data with multilayered functional characteristics of UCA1 knockout/knockdown identified angiomotin (AMOT), a known Hippo-YAP signaling modulator, as potential interacting partner for UCA1. The interaction between UCA1 and AMOT was confirmed using both Western blotting for AMOT using UCA1-iRAP proteins, and RT-qPCR for UCA1 RNA after AMOT immunoprecipitation in 3 independent EOC cell lines. Knockdown experiments showed that AMOT is required for UCA1 to activate the expression of YAP target genes, including CYR61 and AXL. Our results indicate that UCA1 interacts directly with AMOT to promote cell growth by activation of Hippo-YAP signaling in EOC, and for the first time identify UCA1 as a novel upstream regulator of YAP signaling. Moreover, the optimized iRAP method we developed in this study can be readily applied to characterizing the protein, DNA, and RNA interactomes of noncoding or coding transcripts implicated other complex traits. Citation Format: Xianzhi Lin, Tassja J. Spindler, Simon A. Gayther, Kate Lawrenson. Lncrna uca1 interacts directly with angiomotin to activate Hippo-YAP signaling in epithelial ovarian cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 514.