miR-24-3p and miR-27a-3p promote cell proliferation in glioma cells via cooperative regulation of MXI1

MicroRNAs (miRNAs) are small, noncoding RNAs which regulate gene expression at the post-transcriptional level. Abnormal expression of miRNAs occurs frequently in tumors. Although the two miRNAs miR243p and miR27a3p come from two duplicated gene clusters of miR23a~27a~242 and miR23b~27b~241 which are found to be deregulated in a variety of cancers, the role of cooperation of the two clusters and the function of the two miRNAs in tumors have not been completely characterized. Here, we show that overexpression of miR243p and miR27a3p could promote cell proliferation using the MTT assay. By integrated bioinformatic analysis and experimental confirmation, we identified MXI1, which has been found to act as a tumor suppressor gene by affecting cMyc, as a direct target of miR243p and miR27a3p. While targeting the MXI1 3' untranslated region by miR243p or miR27a3p, luciferase activity was attenuated. The two miRNAs promote glioma cell proliferation via targeting MXI1 and the experiment was confirmed by the rescue experiments. Furthermore, our results show that two clusters of miR-23a~27a~24-2 and miR23b~27b~241 regulate MXI1 synergistically. These findings reveal, for the first time, the novel functions of cooperation of miR243p and miR27a3p from two clusters in promoting cell proliferation through MXI1. Additionally, we observed that miR27a3p is upregulated in glioma tissues.