INITIATOR OLIGONUCLEOTIDES FOR THE COMBINATION OF CHEMICAL AND ENZYMATIC RNA-SYNTHESIS

Transcription reactions with T7 RNA polymerase were performed in the p resence of short oligonucleotides (oligos) with guanosine at the 3'-en d. We obtained transcripts which had included these 'initiator oligos' at their 5'-termini. The oligos could contain mixtures of deoxyribo-, ribo-, 2'-O-methylated and biotinylated nucleotides. Only the 3'-term inal guanosine of these oligos was encoded in the template DNA at the transcription start point, in contrast to the remainder of the sequenc e. This 5'-terminal sequence is variable and eliminates the limitation that transcripts must start with a 5'-terminal guanosine. With a 5'-b iotinylated dinucleotide, we obtained end-labeled RNAs suitable for no nradioactive RNA sequencing.