FIG. 4.

Nucleotide preference for de novo initiation of RNA synthesis. The standard SPA assays were performed with one of the following synthetic RNA templates: Rcc (5′ biotin-CGACUACUUACCGAUGGCUGAUUGCGACUACC^di-H 3′) (A), Rct (5′ biotin-CGACUACUUACCGAUGGCUGAUUGCGACUACT^di-H 3′) (B), Rcg (5′ biotin-CGACUACUUACCGAUGGCUGAUUGCGACUACG^di-H 3′) (C), or Rgg (5′ biotin-CGACUACUUACCGAUGGCUGAUUGCGACUAGG^di-H 3′) (D). Two microcurie of ³H-UTP or ³H-CTP was used as the labeling nucleotide. Various concentrations (1.5 to 200 μM) of each individual nucleotide were tested, with the concentrations of the remaining nucleotides at 10 μM.