U2AF Participates in the Binding of TAP (NXF1) to mRNA

• Published in: The Journal of biological chemistry Vol. 277; no. 6; pp. 3935 - 3942
• Main Authors: Zolotukhin, Andrei S., Tan, Wei, Bear, Jenifer, Smulevitch, Sergey, Felber, Barbara K.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 08.02.2002; American Society for Biochemistry and Molecular Biology
• Subjects: Binding Sites; HeLa Cells; Humans; nuclear pore complex; Nuclear Proteins - metabolism; Nucleocytoplasmic Transport Proteins; Protein Binding; Ribonucleoproteins - metabolism; RNA Splicing; RNA, Messenger - metabolism; RNA-Binding Proteins - metabolism; Splicing Factor U2AF; TAP/NXF1 protein; U2AF protein
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M107598200

TAP/NXF1 is a conserved mRNA export receptor serving as a link between messenger ribonucleoproteins (mRNPs) and the nuclear pore complex. The mechanism by which TAP recognizes its export substrate is unclear. We show here that TAP is added to spliced mRNP in human cells. We identified a distinct region of TAP that targets it to mRNP. Using yeast two-hybrid screens and in vitro binding studies, we found that this region coincides with a direct binding site for U2AF35, the small subunit of the splicing factor U2AF. This interaction is evolutionarily conserved across metazoa, indicating its significance. We further found in human cells that the exogenously expressed large U2AF subunit, U2AF65, accumulates in spliced mRNP, leading to the recruitment of U2AF35 and TAP. Similarly to TAP, U2AF65 stimulated directly the nuclear export and expression of an mRNA that is otherwise retained in the nucleus. Together with our finding that U2AF is continuously exported from the nucleus, these data suggest that U2AF participates in nuclear export, by facilitating TAP's addition to its mRNA substrates.