Yasuyuki Hosono, Yashar S. Niknafs, John R. Prensner, Matthew K. Iyer, Saravana M. Dhanasekaran, Rohit Mehra, Sethuramasundaram Pitchiaya, Jean Tien, June Escara-Wilke, Anton Poliakov, Shih-Chun Chu, Sahal Saleh, Keerthana Sankar, Fengyun Su, Shuling Guo, Yuanyuan Qiao, Susan M. Freier, Huynh-Hoa Bui, Xuhong Cao, Rohit Malik, Timothy M. Johnson, David G. Beer, Felix Y. Feng, Weibin Zhou, Arul M. Chinnaiyan

Large-scale transcriptome sequencing efforts have vastly expanded the catalog of long non-coding RNAs (lncRNAs) with varying evolutionary conservation, lineage expression, and cancer specificity. Here, we functionally characterize a novel ultraconserved lncRNA, THOR (ENSG00000226856), which exhibits expression exclusively in testis and a broad range of human cancers. THOR knockdown and overexpression in multiple cell lines and animal models alters cell or tumor growth supporting an oncogenic role. We discovered a conserved interaction of THOR with IGF2BP1 and show that THOR contributes to the mRNA stabilization activities of IGF2BP1. Notably, transgenic THOR knockout produced fertilization defects in zebrafish and also conferred a resistance to melanoma onset. Likewise, ectopic expression of human THOR in zebrafish accelerated the onset of melanoma. THOR represents a novel class of functionally important cancer/testis lncRNAs whose structure and function have undergone positive evolutionary selection.