Figure 4. Addition of Np₄ caps.

(A) Incorporation of AP₄A during transcription initiation. E. coli RNA polymerase was used to synthesize yeiP RNA by in vitro transcription in the presence or absence of a substantial excess of Ap₄A, and the products were examined by boronate gel electrophoresis, with or without prior decapping by RppH (PPase). See also Fig. S6A.

(B) Post-transcriptional capping by lysyl-tRNA synthetase. Triphosphorylated yeiP RNA was treated with purified E. coli LysU in the presence of ATP and lysine, and the reaction products were examined by boronate gel electrophoresis, with or without prior decapping by RppH (PPase). See also Fig. S6B.