Identification of putative microRNA binding sites in the 3'UTR of the proto-oncogene cJun

The proto-oncogene cJun is a regulator of cell proliferation, apoptosis and development.  A component of the immediate–early transcription factor AP-1, cJun was initially discovered as its oncogenic variant vJun, which has transforming mutations in both coding residues and in the 3’ untranslated region (3’ UTR) of the mRNA.  Deletion of the 3’UTR from cJun is sufficient to result in transformation of chicken embryo fibroblasts (CEFs), however the function of the 3’UTR has yet to be described. We obtained the human, mouse, chicken, and rat sequences of the cJun gene from the National Center of Biotechnology Information (NCBI) database and input each into miRwalk, a program designed to search for miRNA binding sites within a nucleotide sequence. Target sites for miRNA-200, 139, 216, and 495 were found in the cJun 3’ UTR of all four species.  Each of these miRNAs has been independently associated with oncogenesis, but none directly correlated to cJun function. We will use mutational analysis and ectopic expression to test the role of these miRNAs on cJun regulation and cellular transformation by AP-1.