miR-1246 releases RTKN2-dependent resistance to UVB-induced apoptosis in HaCaT cells

MicroRNAs are a kind of small non-coding RNAs that play important roles in various biological processes such as cell proliferation, differentiation, and apoptosis. Cellular responses to UV-induced apoptosis have been suggested to be regulated by microRNAs at the posttranscriptional level, while the detailed mechanisms underlying this process remain unclear. Our aim in this study was to investigate the effects of miR-1246 in UVB-induced apoptosis and to identify the functional targets of miR-1246 in keratinocyte HaCaT cells. The expression of miR-1246 and apoptotic genes in HaCaT cells experiencing UVB stress was determined using quantitative real-time PCR. miR-1246 functions in UVB-induced apoptosis were quantified via fluorescence-activated cell sorter analysis of miR-1246 mimic or inhibitor-transfected cells. Additionally, the regulatory relationship between RTKN2 and miR-1246 was identified by Western blot and luciferase reporter assays. miR-1246 was upregulated accompanying with UVB-irradiated apoptosis in HaCaT cells. Overexpression of miR-1246 promoted UVB-induced apoptosis, while knockdown of miR-1246, using a specific inhibitor, resulted in a significant reduction in UVB-elicited apoptosis. We further demonstrate that miR-1246 negatively regulated the expression of RTKN2 through binding to the 3'-untranslated region of RTKN2 at the posttranscriptional level. Moreover, RTKN2 was observed to be resistant to UVB-induced apoptosis and RTKN2 antagonized the pro-apoptotic effects of miR-1246 during UVB-induced apoptosis in HaCaT cells. These findings suggested that miR-1246 promotes UVB-induced apoptosis by downregulating RTKN2 expression and that UVB-upregulated miR-1246 released RTKN2-dependent resistance to UVB-induced apoptosis by targeting RTKN2 post-transcriptionally in keratinocyte cells.