Abstract
MicroRNAs (miRNAs) are a class of short RNAs that regulate gene expression through either translational repression or mRNA cleavage. miRNA-181a (miR-181a), one of the many miRNAs conserved among vertebrates, is differentially expressed in a variety of leukemia. However, its function in leukemia, particularly chronic myelogenous leukemia (CML), is poorly understood. Here we have reported the identification of miR-181a targets by combining TargetScan software prediction and expression profiling through overexpression of miR-181a mimic in leukemic K562 cells. Four overlapping genes were found to be the likely targets of miR-181a. Among the four genes, RalA is a downstream molecule of bcr-abl fusion protein in ras signaling pathway. However, its role in CML remains elusive. Luciferase reporter and Western blot assays confirmed that RalA is a direct target of miR-181a. overexpression of miR-181a effectively suppresses cell growth and induces G2-phase arrest and apoptosis partially by targeting RalA in leukemic K562 cells. Using the KEGG database combined with recent publications, downstream signaling pathway of RalA was graphed by cytoscape software. Therefore, our study is the first to report that RalA is directly regulated by miR-181a and plays an important role in CML. The approach of computational prediction combined with expression profiling might be valuable for the identification of miRNA targets in animal.
Highlights
MicroRNAs are a new class of endogenous noncoding small RNA molecules that have been shown to be important regulators of gene expression in cells. miRNAs post-transcriptionally regulate gene expression by either cleavage or repression of mRNA through binding to the 39-untranslated region (39-UTR) of the target genes [1],[2]
As miRNAs are known to cause degradation or translational repression of target mRNAs, we focused on the genes that are downregulated in miR-181a-transfected cells
The majority of the downregulated genes were found to be involved in the regulation of cell cycle and proliferation, DNA-binding and transcription, metabolism, signal transduction, development, etc. (Table S2.), suggesting that miR-181a may be involved in various aspects of leukemia
Summary
MicroRNAs (miRNAs) are a new class of endogenous noncoding small RNA molecules that have been shown to be important regulators of gene expression in cells. miRNAs post-transcriptionally regulate gene expression by either cleavage or repression of mRNA through binding to the 39-untranslated region (39-UTR) of the target genes [1],[2]. More than 1000 miRNAs have been identified in humans [4]. They are known to be involved in a variety of functions in development, cell proliferation, apoptosis, differentiation, and tumorigenesis [1],[2]. MiRNA functional identification has become one of the most attractive research fields in biomedicine. One major obstacle is to identify the targets regulated by miRNAs. Since there is partial complementarily between miRNAs and their targets in animal cells, the identification of specific target genes for a given miRNA is still a big challenge in our understanding of the miRNA functions. Computation-based approaches for miRNA gene identification and miRNA target prediction are considered as indispensable in miRNA research. Several computational approaches have been developed for the prediction of miRNA targets
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