Figure 1.

Splicing is required for efficient mRNA export. Equal molar amounts of the indicated pre-mRNAs or the corresponding Δi-mRNAs were mixed with U6 snRNA and injected into oocyte nuclei. After incubation at 18°C for the times indicated, oocytes were dissected, and the nucleocytoplasmic distribution of total RNA was analyzed. Data were quantitated by PhosphorImager. The percent mRNA exported was determined by calculating the fraction of mRNA in the cytoplasm relative to the total mRNA at the zero time point (for Δi-mRNAs) or to the total mRNA at the earliest time point when maximal spliced mRNA is present (the 90-min time point for AdML and 60-min time point for Ftz). Note that the graphs for both the Δi-mRNA and the spliced mRNA are plotted beginning with the actual zero time point shown on the gels. Thus, the kinetics of spliced mRNA export are actually faster than indicated in the graphs because the pre-mRNA is spliced before export.