microRNA-16 expression in HeLa cells is upregulated in cell-cycle and drug dependent manner

microRNAs are single-stranded, non-coding RNAs that regulate gene expression. The microRNA-16 family has been reported to be involved in cell-cycle regulation, which could also downregulate expression of multiple pro-proliferation genes. The present results demonstrated that miR-16 expression in HeLa cells increased when the cells were arrested during S-phase under methyl methanesulfate (MMS) treatment. This further resulted in downregulation of a target protein CDC25A, whereas miR-16 expression did not increase when HeLa cells were arrested during the MMS-treated G₀/G₁ or G₂/M phase. Furthermore, when HeLa cells were arrested during S-phase with hydroxyurea treatment, miR-16 expression did not increase. These results suggest that expression levels of microRNAs in mammalian cells are delicately regulated under variable cellular conditions.