The transfection of short interfering RNAs (siRNAs) has revolutionized the study of gene function. siRNA transfections allow researchers to study the phenotypic effects of genes by silencing their expression in cultured cells.
Transfection of long RNAs can be useful for modulating cell phenotype by transiently overexpressing genes, investigating the localization of specific RNAs in living cells, or testing the function of non-coding RNAs. Transfection of longer RNAs introduces a number of complications and is typically lower efficiency than that of small RNA transfection. Key players of the mammalian immune response system recognize exogenous single-stranded RNA (ssRNA) and activate the antiviral defense system. This response results in serious impediment of sustained translation of transfected mRNAs, and even cell death. Incorporation of modified RNA bases in synthetic transcripts has proven to promote mRNA expression and reduced cellular toxicity (1). The ability to efficiently transfect mammalian cells with exogenous mRNA has a number of important implications on cell biology research and medicine.
1. Warren, L., et al (2010) Cell Biology 7, 618-630. PMID: 20888316