Selective labeling and detection of specific RNAs in an RNA mixture.

We report here a unique approach to selectively label and detect specific RNA in an RNA mixture (without separation or purification) using DNA polymerase, dNTP labels, and a short synthetic DNA template complementary to the 3(')-terminus of the RNA. The detection sensitivity is high, at attomole level (10-18 mole). The selective principle was demonstrated by individually labeling and detecting RNAs in a RNA mixture when different templates were provided. By taking advantage of the template-directed selectivity, poly(A) tail-containing mRNA in total RNA was detected and labeled at the 3(')-terminal on a poly(T) template. Nonradioactive labels, such as fluorophore and antigen labels, may also be used; this method can be applied in methodology for direct detection and quantification of viral RNAs.