Figure 6.
Inhibitors of basic NLS import differentially affect U snRNA and mRNA export. Xenopus leavis oocytes were injected into the cytoplasm with the inhibitors indicated above the lanes. As a control, oocytes were injected with PBS alone (lanes 1–6). After 1 h incubation a second microinjection was performed into the oocyte nuclei with a mixture of the following radioactively labeled RNAs: DHFR mRNA, U1ΔSm, U5ΔSm, U6Δss, and human initiator methionyl tRNA. U6Δss does not leave the nucleus and is an internal control for nuclear integrity. Synthesis of DHFR, U1ΔSm, and U5ΔSm RNAs was primed with the m7GpppG cap dinucleotide, whereas synthesis of U6Δss RNA was primed with γ-mGTP. In lanes 4–18 RNA was extracted 150 min after injection; in lanes 1–3, RNA was extracted immediately after injection. The concentration of the inhibitors in the injected samples was as indicated in Fig. 4.