FIG. 4.

Treatment of extract with other forms of guanosine nucleotides has little or no effect on cell-free RNA synthesis. HeLa cytoplasmic extracts were divided evenly and treated with GDPβS, Gpp[NH]p, or GTP, or were mock treated, as detailed in Materials and Methods. Cell-free replication reactions were assembled with the resulting extracts, and viral titer was determined postincubation by standard plaque assay. Bars represent means of duplicate samples.