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Article Title: TAP (NXF1) Belongs to a Multigene Family of Putative RNA Export Factors with a Conserved Modular Architecture
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Figure Lengend Snippet: p15-2a, a human p15-1 homologue, interacts with TAP and localizes to the nuclear rim. (A) Intron-exon structures of p15 family sequences. Protein coding regions and untranslated regions are colored red and white, respectively. The positions of initiation and termination codons are indicated by green and red triangles, respectively. For human p15-2a and -b, the alternative splicing pathway is shown by lines above the gene. The 5′ exon of the p15-2a gene contains an open reading frame of five amino acids, while p15-2b gene 5′ exon sequences contain an in-frame stop codon but no in-frame ATG. Therefore, translation of this mRNA may generate a truncated protein starting at methionine 29 in the p15-2a sequence. Alternatively, translation may start at the GTG codon (green open triangle), resulting in an open reading frame (gray), since this region does not show any similarity to the other p15 sequences. (B) Multiple sequence alignment of p15 family sequences. The symbols are as in Fig. Fig.3.3. (C) Phylogenetic tree of the NTF2 family sequences. The tree was drawn by the neighbor-joining method (34). Abbreviations (other than those in Fig. Fig.11 and and2):2): At, Arabidopsis thaliana; Nt, Nicotiana tabacum; G3BP, Ras-GAP SH3 domain binding protein; MKK3, MAP kinase kinase 3; NPK2, a tobacco protein kinase. (D) Subcellular localization of p15-2a. HeLa cells were transfected with a pEGFP-N3 plasmid derivative expressing a zz fusion of p15-2a. The fusion protein was detected throughout the nucleoplasm and cytoplasm and was excluded from the nucleolus (left). On the right, HeLa cells were extracted with (+) Triton X-100 prior to fixation. A punctate labeling pattern was visible at the nuclear periphery for the p15-2a protein. (E) Lysates from E. coli expressing the Ran binding domain of Importin β (fragment 1–452) or supplemented with equimolar amounts of NTF2, p15-1, or p15-2a were incubated with IgG-Sepharose beads coated with purified zzRanGDP, zzRanQ69L-GTP, or zzTAP (fragment 61–619). After extensive washes, the bound proteins were eluted. One-hundredth of the inputs (lanes 1 to 4) and 1/10 of the bound fractions (lanes 6 to 16) were analyzed by SDS-PAGE followed by Coomassie blue staining. (F) Lysates from E. coli expressing GST fusions of TAP, NXF2, or NXF3 together with untagged versions of p15-1 or p15-2a were incubated with glutathione agarose beads. After extensive washes, the bound proteins were eluted with SDS sample buffer and analyzed by SDS-PAGE followed by Coomassie blue staining. Lanes 1 to 9, input lysates; lanes 11 to 19, bound fractions; lane 10, molecular mass markers (116, 97, 84, 66, 55, 45, 36, 29, 24, 20, and 14.2 kDa).
Article Snippet: For expression of GFP fusions in mammalian cells, NXF2 and NXF3 cDNAs were excised from the pGEMT-easy clones with the restriction enzymes Bam HI/ Hin dIII (NXF2) or Eco RI/ Bam HI (NXF3) and inserted into the vector pEGFP-C1 (Clontech) digested with Bgl II/ Hin dIII or Eco RI/ Bam HI, respectively. pEGFP-N3 (Clontech) derivatives encoding Staphylococcus aureus protein A (zz) fusions of p15-1 and p15-2a were constructed in two steps: first, p15-1 and p15-2a cDNAs were cloned into the vector pRN3zz using the Nco I/ Bam HI restriction sites.
Techniques: Sequencing, Binding Assay, Transfection, Plasmid Preparation, Expressing, Labeling, Incubation, Purification, SDS Page, Staining