Two engineered plasmids are expressed in the living cells. The first one codes for the green
fluorescent protein fused with the RNA-binding protein from the MS2 bacteriophage. The second one
codes for the reporter RNA that contains in its 3'-untranslated region several copies of a unique hairpin
fragment from the MS2 genome that interacts with the MS2 RNA-binding protein. Nuclear
localization signal is also inserted into the protein tag. Binding of the fluorescent tag to the reporter
RNA can generate a strong fluorescent signal [159,160]. Modified target RNA gene can be integrated
into the cell genome by a homologous recombination with PCR-amplified products [161]. This
approach has been used to design several genetically encoded systems for the direct observation of
intracellular RNA dynamics [157]. However, this method is based on artificial gene constructions and
not on natural cell components. It depends on plasmid transfection and intracellular expression of the
tags and reporter RNA. In addition, high background fluorescence is observed in this case.