Phosphorylation regulates the interaction between Gln3p and the nuclear import factor Srp1p.

Carvalho J, Bertram PG, Wente SR, Zheng XF
J Biol Chem. 2001 276 (27): 25359-65

PMID: 11331291 · DOI:10.1074/jbc.M103050200

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.

MeSH Terms (26)

alpha Karyopherins Amino Acid Transport Systems Carrier Proteins Cell Nucleus Cytoplasm DNA-Binding Proteins Drosophila Proteins Electrophoresis, Polyacrylamide Gel Fluorescent Antibody Technique Fluorescent Dyes Fungal Proteins Indoles Karyopherins Mutagenesis, Site-Directed Nitrogen Nuclear Proteins Phosphorylation ras GTPase-Activating Proteins Receptor Protein-Tyrosine Kinases Receptors, Cytoplasmic and Nuclear Repressor Proteins Saccharomyces cerevisiae Proteins Sirolimus Temperature Transcription Factors Yeasts

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