Identification of a novel intergenic miRNA located between the human DDC and COBL genes with a potential function in cell cycle arrest.

Frequent abnormalities in 7p12 locus in different tumors like lung cancer candidate this region for novel regulatory elements. MiRNAs as novel regulatory elements encoded within the human genome are potentially oncomiRs or miR suppressors. Here, we have used bioinformatics tools to search for the novel miRNAs embedded within human chromosome 7p12. A bona fide stem loop (named mirZa precursor) had the features of producing a real miRNA (named miRZa) which was detected through RT-qPCR following the overexpression of its precursor. Then, endogenous miRZa was detected in human cell lines and tissues and sequenced. Consistent to the bioinformatics prediction, RT-qPCR as well as dual luciferase assay indicated that SMAD3 and IGF1R genes were targeted by miRZa. MiRZa-3p and miRZa-5p were downregulated in lung tumor tissue samples detected by RT-qPCR, and mirZa precursor overexpression in SW480 cells resulted in increased sub-G1 cell population. Overall, here we introduced a novel miRNA which is capable of targeting SMAD3 and IGF1R regulatory genes and increases the cell population in sub-G1 stage.