MicroRNA-200b regulates cyclin D1 expression and promotes S-phase entry by targeting RND3 in HeLa cells.

MicroRNAs (miRNAs) are endogenous non-coding small RNAs that inhibit gene expression post-transcriptionally. By regulating their target genes, miRNAs play important roles in tumor generation and development. Recently, the mir-200 family was revealed to inhibit the epithelial-mesenchymal transition, which is viewed as an essential step in early tumor metastasis. Here, we used luciferase assays to demonstrate that mir-200b interacts with predicted target sites in the 3' untranslated region of RND3. In HeLa cells, mir-200b directly reduced the expression of RND3 at the mRNA and protein levels, which thereby promoted expression of the downstream protein cyclin D1 and increased S-phase entry. In conclusion, our study demonstrates a novel role for mir-200b in cell cycle progression and identifies RND3 as a novel mir-200b target.