A feedback expression of microRNA-590 and activating transcription factor-3 in human breast cancer cells

MicroRNAs (miRNAs) are small non coding RNA molecules (∼ 23 nt) that are capable of regulating several physiological and pathological processes by targeting mRNAs post transcriptionally, and miRNAs are also known to be regulated by their own target gene(s) in a feedback manner. In this study, we analysed the expression of miRNAs (pre-mir-93, pre-mir-20b, pre-mir-520 c, pre-mir-143, pre-mir-154 and pre-mir-590) by body map, an in silico method and by qRT-PCR in MDA-MB231 (highly invasive and metastatic in nature), and MCF-7 (poor invasive and metastatic in nature) cells. These miRNAs were down regulated in MDA-MB231 cells, and among these, miR-590 was found to putatively target activating transcription factor-3 (ATF-3), a stress response gene. ATF-3 expression level was significantly increased in MDA-MB231 cells and inhibition of ATF-3 expression in these cells increased the expression of pre-mir-590. Thus, these results suggest that there is a negative feedback expression of pre-mir-590 and its putative target gene, ATF-3 in human breast cancer cells.