Identification and transcriptional regulation of the mir-218-1 alternative promoter

BackgroundmiRNAs are small, endogenous non-coding RNAs approximately 22 nucleotides in length that account for approximately 1% of the genome and play key regulatory roles in multiple signaling pathways. mir-218-1 is an intronic miRNA located within intron 15 of the SLIT2 gene. Public datasets showed enrichment of H3K4me3 within intron 4 of the SLIT2 gene. Therefore, we sought to determine the genomic location and transcriptional regulatory elements of the mir-218-1 candidate alternative promoter in pancreatic ductal adenocarcinoma. MethodsExpression of mir-218 was evaluated in a panel of pancreatic ductal adenocarcinoma cell lines. The mir-218-1 candidate alternative promoter was characterized by chromatin immunoprecipitation, Sequenom, and luciferase assays. Transcriptional regulation of the mir-218-1 candidate alternative promoter was assessed using chromatin immunoprecipitation and an inhibitor to NF-kB. ResultsWe found that expression of mir-218-1 does not correlate with SLIT2 expression and that mir-218-1 has a novel transcriptional start site separate from the SLIT2 promoter. This novel transcriptional start site showed transcriptional activity and was regulated by NF-kB. Conclusionsmir-218-1 is transcribed from an independent and novel transcriptional start site located within intron 4 of the SLIT2 gene in pancreatic ductal adenocarcinoma. Additionally, mir-218-1 expression is regulated by Nf-kB at this alternative transcriptional start site in pancreatic cancer.