Analysis of microRNA expression profiles during the cell cycle in synchronized HeLa cells

Cell cycle progression is regulated by both transcriptional and post-transcriptional mechanisms. MicroRNAs (miRNAs) emerge as a new class of small non-coding RNA regulators of cell cy-cle as recent evidence suggests. It is hypothesized that ex-pression of specific miRNAs oscillates orderly along with cell cycle progression. However, the oscillated expression patterns of many candidate miRNAs have yet to be determined. Here, we describe miRNA expression profiling in double-thymidine synchronized HeLa cells as cell cycle progresses. Twenty-five differentially expressed miRNAs were classified into five groups based on their cell cycle-dependent expression patterns. The cyclic expression of six miRNAs (miR-221, let-7a, miR-21, miR-34a, miR-24, miR-376b) was validated by real-time quan-titative RT-PCR (qRT-PCR). These results suggest that specific miRNAs, along with other key factors are required for main-taining and regulating proper cell cycle progression. The study deepens our understanding on cell cycle regulation. [BMB re-ports 2009; 42(9): 593-598]