Introduction：

microRNAs(miRNA) are a class of endogenous small non-coding single stranded RNAs. One miRNA could regulate multiple protein translation thus regulates broad biological properties. miRNA is highly conserved among species and matured miRNA is approximately 21-24 nucleotides in length. Their roles in diseases, tissue remodeling and cell differentiation have elicited great interest. WZ Biosciences offers over 1,200 human miRNA clones. Human pri-miRNAs were cloned in the pMIR, a special designed mirRNA expression vector. The expression cassette is driven by a CMV promoter and miRNA is expressed as the 3' UTR of GFP.