Use of specific endonuclease cleavage in RNA sequencing

Nonradioactive RNA fragments may be sequenced by incorporation of (3H)-label into 3'-terminal positions, controlled digestion with specific ribonucleases, and separation according to size of the digestion products on polyethyleneimine- (PEI-) cellulose thin layers. This combination of techniques allows one to measure accurately distances of specific cleavage sites from the labeled terminal positions. The cleavage specificities of RNases T1, U2, and A are utilized to identify the positions of G, A, and pyrimidine residues respectively. C and U may be distinguished by mobility differences on PEI-cellulose thin layers at ph 2.6. The procedure is simple, rapid, and highly sensitive; as little as 0.5 - 1 microgram of a RNA of the size of tRNA will be needed to sequence all fragments in a complete RNase digest.