Mature microRNAs identified in highly purified nuclei from HCT116 colon cancer cells

MicroRNAs (miRNAs) have emerged as one of the major regulatory mechanisms of gene expression. A major function of miRNAs involves the post-transcriptional regulation of target mRNAs, which is reported to occur primarily in the cytoplasm. However, there is a significant amount of evidence demonstrating the existence of small non-coding RNAs, including small-interfering RNA (siRNA), miRNA, and Piwi-interacting RNA (piRNA) in the nucleus. In order to elucidate the potential subcellular localizations and functions of miRNAs, we have identified numerous miRNAs that are present in isolated nuclei from human colon cancer HCT116 cells. MicroRNA profiles were compared between cytoplasmic and nuclear fractions of the HCT116 cell line on the basis of multiple microarray analyses. MicroRNA species showing significant existence in isolated and highly purified populations of nuclei were selected and further tested with RT-PCR. The nuclear localization of the mature form of miRNAs was verified again by control RT-PCR ex...