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	Figure 1. eIF-5A is required for nuclear export of GST–Rev–NES and Rev-mediated RNA export, but not for CTE RNA and GST–PKI–NES export in Xenopus oocytes. (A) To analyze interaction of the Rev–NES with eIF-5A in solution, glutathione–Sepharose beads coupled to GST–Rev (lanes 1 and 1′) or, as a control, GST (lanes 2 and 2′) were incubated with the extract of 150 Xenopus oocytes, pelleted, and then processed for immunoblotting with antibodies to eIF-5A. Bound proteins are shown in lanes 1 and 2, and the unbound material are shown in lanes 1′ and 2′. eIF-5A binds specifically to GST–Rev–NES (compare lanes 1 and 1′). Molecular mass standards are indicated in kD. (B) Oocyte injection protocol. After injection and incubation, oocytes were manually dissected in nuclear (N) and cytoplasmic (C) fractions. (C) Proteins were separated by 18% SDS-PAGE, and blots were probed with antibodies against GST and BSA. In the presence of control IgG, within 2 h, most GST–Rev–NES migrates from the nucleus to the cytoplasm (lanes 1 and 2). In contrast, in the presence of antibodies to eIF-5A, the nuclear export of GST–Rev–NES is largely inhibited (lanes 3 and 4). Coinjection of wt eIF-5A protein overcomes the blocking effect of anti–eIF-5A antibodies on GST–Rev–NES export (lanes 5 and 6). To monitor the site of injection, the export substrate was injected along with BSA, which is not exported. The exclusive presence of BSA in the nuclei confirms the specificity of the nuclear injections (lanes 1, 3, and 5). Molecular mass standards are indicated in kD. (D and E) RNA was analyzed by 8 M 6% acrylamide urea gel electrophoresis followed by autoradiography. (D) In the presence of Rev, the RRE RNA is exported (lane 2). In contrast, antibodies against eIF-5A inhibit this export (lane 4). (E) Antibodies against eIF-5A do not prevent the nuclear export of CTE RNA (lanes 2 and 4), indicating that eIF-5A is not involved in the CTE RNA export pathway. Nuclear injected CTE M2/M11 RNA mutant remains in the nuclei (lanes 1 and 3). The nuclear localization of U6-RNA confirms the accuracy of nuclear injections. (F) Nuclear export of the injected GST–PKI–NES fusion protein was analyzed as shown in B. The export of GST–PKI–NES was unaffected by the presence of anti–eIF-5A antibodies (lanes 2 and 4), confirming that eIF-5A is not involved in PKI-NES–mediated nuclear export.
	Figure 2. The eIF-5A mutant protein M14 inhibits the nuclear export of GST–Rev–NES and RRE RNA but not of CTE RNA. (A) Oocyte injection protocol. Before nuclear injection, the export substrate was incubated for 1 h with wt or mutant eIF-5A or, as a control, with PBS alone. (B) Nuclear (N) and cytoplasmic (C) proteins were separated by 18% SDS-PAGE, transferred to nitrocellulose, and probed with antibodies to GST and BSA. In the presence of PBS or wt eIF-5A protein, GST–Rev–NES migrates efficiently to the cytoplasm (lanes 2 and 4). In contrast, the export is blocked in the presence of the eIF-5A mutant M14 (lane 6). The nonexportable protein BSA was injected along with the export substrate to verify the specificity of nuclear injections. Molecular mass standards are indicated in kD. (C and D) RNA was analyzed by 8 M 6% acrylamide urea gel electrophoresis followed by autoradiography. (C) In the presence of PBS or wt eIF-5A, the Rev–RRE RNA is exported (lanes 2 and 4). In contrast, export is inhibited in presence of the mutant protein eIF-5A–M14 (lane 6). (D) Nuclear export of CTE RNA is not prevented by PBS (lane 2), wt eIF-5A (lane 4), or eIF-5A–M14 (lane 6), indicating that eIF-5A is not involved in the CTE RNA export pathway. Nuclear injected CTE M2/M11 mutant RNA remains in the nuclei (lanes 1, 3, and 5). The nuclear localization of U6-RNA confirms the accuracy of nuclear injections.
	Figure 3. The eIF-5A mutant protein M14 is not exported and is unable to bind the export factor CRM1–exportin 1. (A) Oocyte injection protocol. 2 h after nuclear injection of wt eIF-5A or mutant protein M14, oocytes were manually dissected into nuclear (N) and cytoplasmic (C) fractions. (B) Proteins were separated by 18% SDS-PAGE, and blots were analyzed with antibodies to GST and BSA. A substantial fraction of the injected wt GST–eIF-5A migrates into the cytoplasm within 2 h (lane 2). In contrast, most of the eIF-5A mutant protein M14 remains in the nuclei (compare lanes 3 and 4). The exclusive presence of BSA in the nuclei confirms the specificity of the nuclear injections. (C) Interaction of wt eIF-5A and the mutant M14 with CRM1 as determined by pull-down assay. Glutathione–Sepharose beads coupled to the GST proteins indicated were incubated with oocyte extract. Bound and unbound proteins were resolved by SDS-PAGE and analyzed by immunoblotting experiments with anti-CRM1 antiserum. Bound proteins are shown in lanes 1–3, unbound proteins are shown in lanes 1′–3′. CRM1 binds to the wt form of eIF-5A (lane 1) but not to the M14 mutant (lane 2) and GST alone (lane 3). (D) Role of eIF-5A for interaction between CRM1 and Rev–NES was analyzed by pull-down assay. GST–Rev–NES coupled to glutathione–Sepharose beads was incubated with wt eIF-5A/eIF-5A–M14 before incubation with oocyte extract. Bound (lanes 1–3) and unbound (1′–3′) proteins were analyzed as described above. CRM1 binds to GST–Rev–NES only in the presence of the wt form of eIF-5A (lane 1) but not of the M14 mutant (lane 2). (E) Role of eIF-5A for interaction between recombinant CRM1 fusion protein and Rev–NES was analyzed by pull-down assay. GST–Rev–NES or GST alone coupled to glutathione-Sepharose beads were incubated in various combinations with RanGTP (GST-RanQ69L), wt eIF-5A, or eIF-5A–M14 before addition of recombinant His-tagged CRM1. Bound (lanes 1–5) and unbound (lanes 1′–5′) CRM1 was visualized by using His-specific antibodies. CRM1 fusion protein binds to GST–Rev–NES only in the presence of the wt form of eIF-5A and RanGTP (lane 1 versus lanes 3 and 5) but not in presence of the M14 mutant (lane 2) and not to GST (lane 4). The 66- and 45-kD components apparently represent CRM1 degradation products. Molecular mass standards are indicated in kD.
	Figure 4. Interaction of eIF-5A with nuclear envelope proteins as determined by overlay assays and pull-down experiments. (A) Nuclear envelopes were manually isolated from Xenopus oocytes, and the proteins were separated by 12% SDS-PAGE, transferred to nitrocellulose, and incubated with GST alone (lane 1) or GST–eIF-5A fusion protein (lanes 2–5). eIF-5A binds to eight polypeptide bands as revealed by anti-GST antibodies (indicated by dots, lane 2). Membranes were then stripped of bound antibodies and reprobed with antibodies to CRM1 (lane 3), to a family of nucleoporins (mAb 414, lane 4), and to actin (lane 5). The eIF-5A binding proteins identified are indicated at the right. (B) To analyze interactions of eIF-5A with nuclear proteins in solution, glutathione–Sepharose beads coupled to GST–eIF-5A (lanes 1–5) or to GST (lanes 6 and 7) were incubated with the extract of 150 manually isolated nuclei of Xenopus oocytes. The bound pelleted proteins were analyzed by immunoblotting (lanes 1–3) with antibodies to CRM1 (lane 1), nucleoporins (lane 2), and actin (lane 3), or by silver staining (lanes 4 and 6). The unbound proteins were visualized by silver staining (lanes 5 and 7). Molecular mass standards are indicated in kD.
	Figure 5. Actin is a constituent of the nucleoplasmic NPC-associated filaments as shown by immungold electron microscopy. Manually isolated nuclear envelopes from Xenopus (A) and Pleurodeles (B) oocytes were incubated with antiactin antibody 2G2 followed by secondary antibodies coupled to 12-nm gold particles. The nuclear filaments extending from the NPCs are particularly prominent in Pleurodeles oocytes (B). The occasional presence of mitochondria (M) clearly identifies the cytoplasmic side of the nuclear envelope. ONM, outer nuclear membrane; INM, inner nuclear membrane. Bars, 0.3 μm.
	Figure 7. Different effects of actin-binding drugs on nuclear export of GST–Rev–NES and GST–PKI–NES. (A) Oocyte injection protocol. 1 h after nuclear injection of latrunculin B, swinholide A or PBS (control) and the export substrate GST–Rev–NES or GST–PKI–NES, together with BSA, were microinjected into oocyte nuclei. 2 h later, oocytes were manually dissected into nuclear (N) and cytoplasmic (C) fractions. (B and C) Proteins were separated by 18% SDS-PAGE, and blots were analyzed with antibodies to GST and BSA. A substantial fraction of the injected export substrate migrates into the cytoplasm in the presence of PBS (lane 2) or swinholide A (lane 6). In contrast, the export substrate remains exclusively in the nuclei in presence of latrunculin B (lane 3). Detection of BSA in the nuclei confirms the specificity of the nuclear injections.
	Figure 6. Antibodies against actin inhibit nuclear export of GST–Rev–NES, GST–PKI–NES, RRE RNA, and CTE RNA in Xenopus oocytes. (A) Oocyte injection protocol. Nuclear (N) and cytoplasmic (C) fractions were manually isolated. (B and E) Proteins were separated by 18% SDS-PAGE and analyzed by immunoblotting with antibodies to GST and BSA. The exclusive presence of the nonexportable protein BSA in the nuclear fractions confirms the accuracy of the injections. (B) The nuclear export of GST–Rev–NES is strongly inhibited by antibodies against actin (lane 4) but not by control IgM (lane 2). (E) Antiactin antibodies also block the nuclear export of GST–PKI–NES (lane 4), whereas, in contrast, it is exported in the presence of control IgM (lane 2). Molecular mass standards are indicated in kD. (C and D) RNA separated by 8 M 6% acrylamide urea gels and visualized by autoradiography. (C) In the presence of antiactin antibodies, the Rev-mediated export of RRE RNA is inhibited (compare lanes 2 and 4). (D) Antiactin antibodies also inhibit the export of CTE RNA (compare lanes 2 and 4). As expected, the mutant CTE M2/M11 is not exported (lanes 1 and 3). The nuclear localization of the nonexportable U6 RNA confirms the accuracy of the nuclear injections.
	Figure 9. Nuclear export of Rev in a cell-free system. Nuclei were isolated from a HeLa cell line that constitutively expresses high levels of nuclear HIV-1-Rev and were incubated in Xenopus egg extract with or without cytochalasin B and an energy-regenerating system. After 1 h, nuclei were processed for immunofluorescence with antibodies to Rev (A′′–D′′) and counterstained with the DNA-specific dye Hoechst (A′–D′). In the absence of cytochalasin B and the presence of energy, Rev is exported from the nuclei (C′′). The corresponding phase–contrast images are shown (A–D). Bars, 15 μm.
	Figure 8. Inhibition of nuclear export of GFP–Rev–NES–GST fusion protein by antiactin antibodies in cultured Vero cells. A mixture of GFP–Rev–NES–GST fusion protein, together with either control IgM (A and B), or antiactin antibodies (C and D) was microinjected into nuclei of Vero cells. Phase–contrast images (left) and GFP fluorescence (right) were recorded at the indicated postinjection time points. The export substrate is efficiently translocated from the nucleus to the cytoplasm in the presence of control IgM (A′ and B′). In contrast, coinjected antiactin antibodies completely prevent nuclear export (C′ and D′). Microinjected cells are denoted by arrows. Bar, 20 μm.

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