An alternative microRNA-mediated post-transcriptional regulation of GADD45A by p53 in human non-small-cell lung cancer cells

GADD45A (growth arrest and DNA damage inducible alpha), a stress response gene induced by genotoxic and nongenotoxic stresses, is implicated in various key processes, including the control of cell cycle checkpoints and DNA repair. The expression of GADD45A is directly regulated by numerous transcription factors, with p53 being the most representative. Moreover, post-transcriptional regulation also plays a role in GADD45A expression. However, little is known about the regulatory effects of microRNAs (miRNAs) on GADD45A expression. As a potential tumour suppressor, miR-138 has pleiotropic biological functions in various cancers. We have previously reported p53-mediated activation of miR-138 in human non-small-cell lung cancer (NSCLC) cells. In this study, we found that miR-138 specifically targeted AGO2, which affects the stability and maturation of miR-130b. Decreased expression of miR-130b promoted the expression of GADD45A and resulted in the G2/M phase arrest and proliferation inhibition in human NSCLC cells. Our results suggested that p53 could alternatively upregulate GADD45A in human NSCLC cells through a post-transcriptional pathway in which miR-138 is involved.