Published in

American Association for Cancer Research, Cancer Research, 14(79), p. 3570-3582, 2019

DOI: 10.1158/0008-5472.can-18-2403

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The Promoter-Associated Noncoding RNA pncCCND1_B Assembles a Protein–RNA Complex to Regulate Cyclin D1 Transcription in Ewing Sarcoma

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Abstract

Abstract Most Ewing sarcomas are characterized by the in-frame chromosomal translocation t(11;22) generating the EWS–FLI1 oncogene. EWS–FLI1 protein interacts with the RNA helicase DHX9 and affects transcription and processing of genes involved in neoplastic transformation, including CCND1 (the cyclin D1 gene), which contributes to cell-cycle dysregulation in cancer. In this study, we found that CCND1 expression is significantly higher in patients with Ewing sarcoma compared with other sarcomas and that the pncCCND1_B RNA, a previously uncharacterized CCND1 promoter-associated noncoding (pnc) transcript, is expressed in Ewing sarcoma cells. PncCCND1_B interacted with the RNA-binding protein Sam68 and repressed CCND1 expression. Notably, knockdown of Sam68 affected pncCCND1_B subcellular localization and cyclin D1 expression. Pharmacologic impairment of DHX9/EWS–FLI1 interaction promoted RNA-dependent association of Sam68 with DHX9 and recruitment of Sam68 to the CCND1 promoter, thus repressing it. Conversely, mitogenic stimulation of Ewing sarcoma cells with IGF1 impaired Sam68/DHX9 interaction and positively regulated CCND1 expression. These studies uncover a fine-tuned modulation of the proto-oncogene CCND1 in Ewing sarcoma cells via alternative complexes formed by DHX9 with either EWS–FLI1 or pncCCND1_B-Sam68. Significance: A pncRNA-based mechanism represses expression of CCND1 through the formation of a protein–RNA complex and provides new therapeutic opportunities for patients with Ewing sarcoma.