Regulation of long non-coding RNA expression by aryl hydrocarbon receptor activation

The aryl hydrocarbon receptor (AhR) is a cytosolic transcription factor that can be activated by endogenous or xenobiotic ligands. Upon activation, the AhR translocates to the nucleus, dimerizes with the AhR nuclear translator (ARNT), and binds to specific DNA sequences called xenobiotic response elements (XRE) to promote target gene transcription, including cytochrome P450 (e.g., CYP1A1) expression. In addition to mRNA, the AhR may also regulate long non-coding RNA (lncRNA) expression. lncRNA are transcripts more than 200 nucleotides in length that do not encode a protein. Herein, we tested whether AhR activation regulates the expression of lncRNA in response to benzo[a]pyrene (B[a]P) using RNA sequencing (RNA-seq). We found that many lncRNA (e.g., SATB1-AS1, MIR4290HG, AC008969.1, LINC01533, VIPR1-AS1) and protein-coding RNA (e.g., CYP1A1, BX005266.2, AQP3, BTG2, DCX, and AhRR) were differentially expressed (DE) in A549 cells treated with B[a]P; many of these genes were dependent on AhR expression including CYP1A1, CYP1B1 and TiPARP. GO analyses indicated that DE protein-coding RNAs in A549^WT cells are associated with distinct molecular functions compared to A549^KO cells. KEGG analyses showed the hsa01100 pathway was associated with DE lncRNA only in A549^WT cells. A549^KO cells treated with B[a]P exhibited a distinct set of differentially-regulated lncRNA including upregulation of HOTAIR. We further confirmed that despite AhR activation in A549^WT cells, B[a]P did not alter the expression of many well-characterized lncRNA including NEAT1, HOTTIP, SOX2OT, MALAT1, H19, and Linc00673. Thus, there is control over select lncRNA expression in A549 cells exposed to B[a]P, a finding which could yield insight into the molecular function of the AhR.