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Phosphorylation regulates the interaction between Gln3p and the nuclear import factor Srp1p
J Carvalho1, P G Bertram, S R Wente
1Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
The Journal of Biological Chemistry
|May 2, 2001
Summary
Gln3p nuclear transport is regulated by phosphorylation. Yeast karyopherin alpha (Srp1p) and Crm1p mediate Gln3p import and export, respectively, impacting nitrogen catabolite repression.
Area of Science:
- Molecular Biology
- Cell Biology
- Genetics
Background:
- Gln3p, a GATA-type transcription activator, regulates nitrogen catabolite repressible (NCR) genes.
- Gln3p phosphorylation is TOR-dependent, sequestering it in the cytoplasm under nutrient-rich conditions.
- Nitrogen starvation or rapamycin treatment causes Gln3p dephosphorylation and nuclear accumulation, activating NCR genes.
Purpose of the Study:
- To elucidate the mechanism regulating Gln3p nucleocytoplasmic distribution.
- To identify the specific nuclear transport factors involved in Gln3p translocation.
Main Methods:
- Functional genomics approach to identify nuclear transport factors.
- Investigated the roles of yeast karyopherin alpha (Srp1p) and Crm1p in Gln3p transport.
- Examined the involvement of the Ran GTPase pathway.
Main Results:
- Yeast karyopherin alpha (Srp1p) is essential for Gln3p nuclear import.
- Crm1p mediates the nuclear export of Gln3p.
- The Ran GTPase pathway is implicated in Gln3p nuclear translocation.
- Srp1p exhibits preferential binding to hypophosphorylated Gln3p.
Conclusions:
- Phosphorylation status of Gln3p dictates its interaction with Srp1p, regulating nuclear import.
- Srp1p and Crm1p, along with the Ran GTPase pathway, orchestrate Gln3p's dynamic nucleocytoplasmic shuttling.
- This provides a mechanistic framework for how Gln3p's phosphorylation state controls its function in nitrogen metabolism.
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