Figure 9

Following AMP during ligation reactions with T4 RNA ligases. (A) 22-mer DNA adapters were 5'-adenylated with α-³²P-labeled ATP (see materials and methods). Intermolecular strand-joining reactions containing 10 pmol radiolabeled DNA adapter, 5 pmol 21-mer 5'-PO₄ RNA acceptor, and ligase (1 pmol) were incubated overnight at 16°C in the presence of PEG 8000. Reaction products were resolved on a denaturing 15% acrylamide gel and radioactive molecules were visualized by exposure to Phosphor screens. The resulting products were either free AMP in solution (AMP*) or the adapter remaining adenylated (Ap*p-DNA). Oligonucleotide substrates are depicted schematically above the gel. Grey lines represent RNA and black lines represent DNA. P* denotes ³²P-phosphate. (B) Determining the fate of AMP upon T4 RNA ligase-dependent deadenylation. Reactions containing radiolabeled DNA adapter (10 pmol) and ligase (14 pmol) were incubated overnight at 16°C in the presence of 12.5% PEG 8000. Oligonucleotide substrates are depicted schematically above the gel. P* denotes ³²P-phosphate. Reaction products were resolved and visualized as in (A). The resulting products were either free AMP in solution (AMP*), the adapter remaining adenylated (Ap*p-DNA), or AMP covalently bound to the ligase (AMP*-ligase). The lane labeled input contains only Ap*p-DNA. (C) Reactions identical to those in (B) were treated with Proteinase K prior to gel electrophoresis and detection. (D) Reactions containing 10 pmol radiolabeled DNA adapter, 5 pmol 28-mer [5'-PO₄, 3'-blocked] RNA acceptor, and ligase (1 pmol) were incubated, resolved and detected as in (A). The resulting products were either free AMP in solution (AMP*), adenylated adapter (Ap*p-DNA), or Ap*p-28-mer RNA. The lane labeled RNA size control contains 5'-³²PO₄ RNA, and the lane labeled input contains only Ap*p-DNA. Oligonucleotide substrates are depicted schematically above the gel. Grey lines represent RNA and black lines represent DNA. P* denotes ³²P-phosphate. In all panels, Rnl1 = T4 RNA ligase 1, Rnl2 = T4 RNA ligase 2, Rnl2tr = T4 RNA ligase 2 truncated, Rnl2 +MBP = T4 RNA ligase 2 truncated attached to an N-terminal maltose binding protein tag. All mutations indicated are substitutions in T4 Rnl2tr + MBP.