Studies of the regulatory function of microRNA-221/222 on the expression of HIF-1β
Date Issued
2008
Date
2008
Author(s)
Pan, Guo-Wei
Abstract
MicroRNAs (miRNAs) are non-coding, single-stranded RNAs of 21～23 nucleotides in length, which suppress the expressions of target genes through translational repression or mRNA cleavage. MiRNAs involve in the regulations of many important cellular activities, including embryo development, cell differentiation, tumorigenesis, and tumor cell proliferation, etc.. Previous investigations have shown that the expressions of microRNA-221 and microRNA-222 (miR-221/222) significantly elevate in the oncogenetic processes of several cancers; thus we focus on miR-221/222 in the present investigation. First, we searched for the potential target genes of miR-221/222 in miRNA databanks. HIF-1β was selected for further investigation. HIF-1β is one of the two subunits that constitute HIF-1 (hypoxia-inducible factor-1) transcription factor, which plays significant roles in many cellular activities.e employed gastrointestinal cancer cell lines as study models to investigate whether miR-221/222 regulate the expression of HIF-1β. MiR-221/222 mimics and specific inhibitors for miR-221/222 were transfected into the gastrointestinal cancer cells, and western blotting analyses for the expressions of HIF-1β were followed. The results demonstrated the inhibitory function of miR-221/222 on HIF-1β expression. In the successive experiments, the reporter plasmids bearing the 3’-untranslated region (3’-UTR) fragments, wild-type or miR-221/222-seed site mutated, of HIF-1β gene were constructed, and the results obtained from the reporter gene activity assays of the constructs suggested that HIF-1β gene is the target of miR-221/222. In addition, the expressions of HIF-1β transcript in the cell models were quantitatively analyzed through real-time RT-PCR to elucidate which mechanism, translational repression or mRNA cleavage, leading to the suppression of HIF-1β-protein expression by miR-221/222.ur investigations demonstrate that miR-221/222 can inhibit the expression of HIF-1β. This suggests a novel route through which the activity of HIF-1 transcription factor could be regulated.s the significant elevation of miR-221/222 expressions in pancreatic cancer has been well documented, we used miRNA inhibitors to neutralize the endogenous miR-221/222 in pancreatic cancer cell lines, and employed human-nude mice xenograft model to examine the effects of miR-221/222 on the tumor formation of pancreatic cancer cells. However, opposite results were observed from the experiments of two different cell lines, with significant inhibition of tumor formation observed in one cell line while promotion in the other. More studies are expected for further exploration on this subject; nonetheless, the two opposite results obtained from the two cell lines both demonstrate the significant role of miR-221/222 in pancreatic cancer.
Subjects
MicroRNA
HIF-1β
SDGs
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