Kap104p imports the PY-NLS-containing transcription factor Tfg2p into the nucleus.
A previous bioinformatics study identified a putative PY-NLS in the yeast transcription factor Tfg2p (Suel, K. E., Gu, H., and Chook, Y. M. (2008) PLoS Biol. 6, e137). In this study, we validate Tfg2p as a Kap104p substrate and examine the energetic organization of its PY-NLS. The Tfg2p PY-NLS can target a heterologous protein into the cell nucleus through interactions with Kap104p. Surprisingly, full-length Tfg2p is still localized to the nucleus of Kap104p temperature-sensitive cells and, similarly, Tfg2p with a mutated PY-NLS is nuclear in wild-type cells. Other Karyopherinbetas (Kapbetas) such as Kap108p and Kap120p also bind Tfg2p and may import it into the nucleus. More importantly, we demonstrate that Tfg2p is retained in the nucleus through DNA binding. Mutations of DNA binding residues relieve nuclear retention and unmask the role of Kap104p in Tfg2p nuclear import. More generally, steady-state localization of a nuclear protein is dictated by its nuclear import and export activities as well as its interactions in the nucleus and the cytoplasm.
Süel
Katherine E
KE
Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
Chook
Yuh Min
YM
D000595:Amino Acid Sequence; D001665:Binding Sites; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005982:Glutathione Transferase / Q000235:genetics; D028884:Karyopherins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000235:genetics; D010957:Plasmids; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics*; D028961:beta Karyopherins
C101820:KAP104 protein, S cerevisiae; D028884:Karyopherins; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D028961:beta Karyopherins; D005982:Glutathione Transferase