HYBRID SELECTION WITH CDNA-SILICA

A partial length ovalbumin cDNA-silica was produced using primer exten sion of (dT)18-silica with annealed partial ovalbumin RNA and reverse transcriptase. This cDNA-silica was used to test whether full-length o valbumin RNA could be selectively purified in the presence of a large excess of other (mouse muscle) RNA. The cDNA-silica synthesized had mi nimally 60 pmol cDNA per gram silica and had a capacity for full-lengt h ovalbumin RNA of minimally 38 mu g/g. Even when other RNA was presen t in greater than 1000-fold excess, ovalbumin RNA was selectively reta ined by the cDNA-silica and was eluted in yields of 43% with an enrich ment which varied over the range of 29-162-fold in various experiments . These results show that even rare RNAs can be selectively purified i n high yield using cDNA-silica. The importance of these results to hyb rid selection and subtractive library preparation is discussed.