Phosphorylation regulates the interaction between Gln3p and the nuclear import factor Srp1p.
Gln3p is a GATA-type transcription activator of nitrogen catabolite repressible (NCR) genes. Gln3p was recently found to be hyperphosphorylated in a TOR-dependent manner and resides in the cytoplasm in high quality nitrogen. In contrast, during nitrogen starvation or rapamycin treatment, Gln3p becomes rapidly dephosphorylated and accumulates in the nucleus, thereby activating nitrogen catabolite repression genes. However, a detailed mechanistic understanding is lacking for the regulation of Gln3p nucleocytoplasmic distribution. In this study, we applied a functional genomics approach to identify the nuclear transport factors for Gln3p. We found that yeast karyopherin alpha/Srp1p and Crm1p are required for the nuclear import and export of Gln3p, respectively. Similarly, the Ran GTPase pathway is also involved in the nuclear translocation of Gln3p. Finally, we show that Srp1p preferentially interacts with the hypophosphorylated versus the hyperphosphorylated Gln3p. These findings define a possible mechanism for regulated nucleocytoplasmic transport of Gln3p by phosphorylation in vivo.
Carvalho
J
J
Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Bertram
P G
PG
Wente
S R
SR
Zheng
X F
XF
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D029721:Drosophila Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D005456:Fluorescent Dyes; D005656:Fungal Proteins / Q000378:metabolism*; D007211:Indoles; D028884:Karyopherins; D016297:Mutagenesis, Site-Directed; D009584:Nitrogen / Q000502:physiology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus / Q000494:pharmacology; D013696:Temperature; D014157:Transcription Factors; D015003:Yeasts; D028901:alpha Karyopherins; D020703:ras GTPase-Activating Proteins / Q000235:genetics; D000097606:Exportin 1 Protein
D026905:Amino Acid Transport Systems; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005456:Fluorescent Dyes; D005656:Fungal Proteins; D007211:Indoles; D028884:Karyopherins; D009584:Nitrogen; D009687:Nuclear Proteins; D020794:Receptor Protein-Tyrosine Kinases; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; D014157:Transcription Factors; D028901:alpha Karyopherins; D020703:ras GTPase-Activating Proteins; D000097606:Exportin 1 Protein; C491145:GAP1 protein, S cerevisiae; C071664:GLN3 protein, S cerevisiae; C491146:RasGAP1 protein, Drosophila; C007293:DAPI; C080148:tor protein, Drosophila