FIGURE 2.

Possible reaction products from 5′-adenylation of an RNA substrate with T4 RNA ligase and ATP. 5′-monophosphate and 5′-adenyl pyrophosphate termini are abbreviated p and App, respectively. The 5′-to-3′ polarity of each strand is shown by an arrowhead pointing in the 3′-direction. The desired 5′-AppRNA is boxed, and the three possible side reactions starting from 5′-AppRNA are illustrated (circularization, oligomerization, and blocking oligo ligation). The abbreviations used for the other products in the remaining figures of this article are given in boldface within parentheses. For the oligomerization reaction, the RNA substrate that does not provide the reactive 5′-App may itself have either 5′-p or 5′-App. Therefore, two different oligomerization products of any given nucleotide length are possible; only one is shown here.