A novel nuclear import pathway for the transcription factor TFIIS.
We have identified a novel pathway for protein import into the nucleus. We have shown that the previously identified but uncharacterized yeast protein Nmd5p functions as a karyopherin. It was therefore designated Kap119p (karyopherin with Mr of 119 kD). We localized Kap119p to both the nucleus and the cytoplasm. We identified the transcription elongation factor TFIIS as its major cognate import substrate. The cytoplasmic Kap119p exists as an approximately stoichiometric complex with TFIIS. RanGTP, not RanGDP, dissociated the isolated Kap119p/TFIIS complex and bound to Kap119p. Kap119p also bound directly to a number of peptide repeat containing nucleoporins in overlay assays. In wild-type cells, TFIIS was primarily localized to the nucleus. In a strain where KAP119 has been deleted, TFIIS was mislocalized to the cytoplasm indicating that TFIIS is imported into the nucleus by Kap119p. The transport of various substrates that use other karyopherin-mediated import or export pathways was not affected in a kap119Delta strain. Hence Kap119p is a novel karyopherin that is responsible for the import of the transcription elongation factor TFIIS.
Albertini
M
M
Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, New York 10021, USA.
Pemberton
L F
LF
Rosenblum
J S
JS
Blobel
G
G
D002467:Cell Nucleus / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D005656:Fungal Proteins / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D017353:Gene Deletion; D005800:Genes, Fungal; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007700:Kinetics; D009687:Nuclear Proteins / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity; D014157:Transcription Factors / Q000302:isolation & purification / Q000378:metabolism*; D035165:Transcription Factors, General; D035602:Transcriptional Elongation Factors; D020931:ran GTP-Binding Protein
D005656:Fungal Proteins; D009687:Nuclear Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D035165:Transcription Factors, General; D035602:Transcriptional Elongation Factors; C018648:transcription factor S-II; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D019204:GTP-Binding Proteins; D020931:ran GTP-Binding Protein