Wnt activated β-catenin and YAP proteins enhance the expression of non-coding RNA component of RNase MRP in colon cancer cells.

RMRP, the RNA component of mitochondrial RNA processing endoribonuclease, is a non-coding RNA (ncRNA) part of the RNase MRP complex functioning in mitochondrial and ribosomal RNA processing. Even though various mutations in the RMRP gene are linked to developmental defects and pathogenesis, its relevance to cancer etiology has not been well established. Here we examined the expression of RMRP and found a significant increase in colorectal and breast cancer patient tissues. So we tested whether the oncogenic signaling pathways, Wnt/β-catenin and Hippo/YAP pathways, are relevant to the enhanced expression of RMRP in cancer cells because of the predicted β-catenin/TCF and YAP/TBX5 elements in the upstream regions of the RMRP gene. As expected, Wnt signal activation significantly induced the RMRP transcription thru β-catenin and YAP transcription factors. More importantly, YAP protein was critical for RMRP transcription by association to the proximal site near the transcription start site of the RMRP gene, a Pol III promoter, along with β-catenin and TBX5 proteins. We propose that the interplay of Wnt and Hippo signaling pathways could regulate target genes, coding or non-coding, by the β-catenin/YAP/TBX5 transcription complex in cancer cells.