KDM6A-Mediated Expression of the Long Noncoding RNA DINO Causes TP53 Tumor Suppressor Stabilization in Human Papillomavirus 16 E7-Expressing Cells

Abstract

HPV16 E7 has long been noted to stabilize the TP53 tumor suppressor. However, the molecular mechanism of TP53 stabilization by HPV16 E7 has remained obscure and can occur independent of E2F regulated MDM2 inhibitor, p14^ARF. Here, we report that the Damage Induced Noncoding (DINO) lncRNA (DINOL) is the missing link between HPV16 E7 and increased TP53 levels. DINO levels are decreased in cells where TP53 is inactivated, either by HPV16 E6, expression of a dominant negative TP53 minigene or by TP53 depletion. DINO levels are increased in HPV16 E7 expressing cells. HPV16 E7 causes increased DINO expression independent of RB1 degradation and E2F1 activation. Similar to the adjacent CDKN1A locus, DINO expression is regulated by the histone demethylase, KDM6A. DINO stabilizes TP53 in HPV16 E7 expressing cells and as a TP53 transcriptional target, DINO levels further increase. Similar to other oncogenes such as adenovirus E1A or MYC, HPV16 E7 expressing cells are sensitized to cell death under conditions of metabolic stress which, in the case of E7 has been linked to TP53 activation. Consistent with earlier studies, we show that HPV16 E7 expressing keratinocytes are highly sensitive to metabolic stress induced by starvation or the antidiabetic drug, metformin. Metabolic stress sensitivity of HPV16 E7 expressing cells to is rescued by DINO depletion. Moreover, DINO depletion decreases sensitivity to the DNA damage inducing chemotherapy agent, doxorubicin. This work identifies DINO as a critical mediator TP53 stabilization and activation in HPV16 E7 expressing cells. IMPORTANCEViral oncoproteins, including HPV16 E6 and E7 have been instrumental in elucidating the activities of cellular signaling networks including those governed by the TP53 tumor suppressor. Our study demonstrates that the long noncoding RNA DINO is the long sought missing link between HPV16 E7 and elevated TP53 levels. Importantly, the TP53 stabilizing DINO plays a critical role in the cell death response of HPV16 E7 expressing cells to metabolic stress or DNA damage.