Antisense RNAs Influence Promoter Usage of Their Counterpart Sense Genes in Cancer.

Abstract

Multiple noncoding natural antisense transcripts (ncNAT) are known to modulate key biological events such as cell growth or differentiation. However, the actual impact of ncNATs on cancer progression remains largely unknown. In this study, we identified a complete list of differentially expressed ncNATs in hepatocellular carcinoma. Among them, a previously undescribed ncNAT <i>HNF4A-AS1L</i> suppressed cancer cell growth by regulating its sense gene <i>HNF4A</i>, a well-known cancer driver, through a promoter-specific mechanism. <i>HNF4A-AS1L</i> selectively activated the <i>HNF4A</i> P1 promoter via HNF1A, which upregulated expression of tumor suppressor P1-driven isoforms, while having no effect on the oncogenic P2 promoter. RNA-seq data from 23 tissue and cancer types identified approximately 100 ncNATs whose expression correlated specifically with the activity of one promoter of their associated sense gene. Silencing of two of these ncNATs <i>ENSG00000259357</i> and <i>ENSG00000255031</i> (antisense to <i>CERS2</i> and <i>CHKA</i>, respectively) altered the promoter usage of <i>CERS2</i> and <i>CHKA</i>. Altogether, these results demonstrate that promoter-specific regulation is a mechanism used by ncNATs for context-specific control of alternative isoform expression of their counterpart sense genes. SIGNIFICANCE: This study characterizes a previously unexplored role of ncNATs in regulation of isoform expression of associated sense genes, highlighting a mechanism of alternative promoter usage in cancer.