JMJD6 induces HOTAIR, an oncogenic lincRNA, by physically interacting with its proximal promoter

Using microarray analysis, we found that HOX transcript antisense intergenic RNA (HOTAIR) is up-regulated by Jumonji domain containing-6 (JMJD6), a bifunctional lysyl hydroxylase and arginine demethylase. In breast cancer, both JMJD6 and HOTAIR RNAs increase tumor growth and associate with poor prognosis but no molecular relationship between them is known. We show that overexpression of JMJD6 increased HOTAIR expression and JMJD6 siRNAs suppressed it in ER+ MCF-7, triple negative MDA-MB-231 and non-breast cancer HEK 293 cells. Therefore, JMJD6 regulates HOTAIR independent of ER status. Using various deletion constructs spanning (-1874 to +50) of the HOTAIR promoter, we identified pHP216 (-216 to +50 bp) as the smallest construct that retained maximal JMJD6 responsiveness. In ChIP assays, JMJD6 bound this region suggesting that JMJD6 may be directly recruited to the HOTAIR promoter. Mutant JMJD6H187A that is devoid of enzymatic activity could bind this site but failed to induce transcription. ChIP and electromobility shift assays identified a JMJD6 interaction region from (-123 to -103 bp) within the HOTAIR promoter. In tumor samples but not normal breast tissue, the expression of JMJD6 linearly correlated with HOTAIR suggesting that JMJD6-mediated up-regulation may occur specifically in tumors. Further, concurrent high expression of both genes correlated with poor survival when individual expression of either gene showed no significant association in TCGA datasets. We propose that high JMJD6 expression may achieve higher levels of HOTAIR in breast tumors. Further, since high levels of HOTAIR promote metastasis and death, blocking JMJD6 may be useful in preventing such events.