Abstract
In metazoan cells, the CAS protein has been shown to function as a recycling factor for the importin-alpha subunit of the classical nuclear localization signal receptor, exporting importin-alpha from the nucleus to allow its participation in multiple rounds of nuclear import. CAS is a member of a family of proteins that bear homology to the larger subunit of the nuclear localization signal receptor, importin-beta, and that are found in all eukaryotes from yeast to humans. Sequence similarity identifies the product of the Saccharomyces cerevisiae CSE1 gene as a potential CAS homologue. Here we present evidence that Cse1p is the functional homologue of CAS: Cse1p is required to prevent accumulation of Srp1p/importin-alpha in the nucleus, it localizes to the nuclear envelope in a pattern typical of nuclear transport receptors, and it associates in vivo with Srp1p in a nucleotide-specific manner. We show further that mutations in CSE1 and SRP1 have specific effects on their association and on the intracellular localization of Cse1p.
Publication types
-
Research Support, Non-U.S. Gov't
-
Research Support, U.S. Gov't, P.H.S.
MeSH terms
-
Biological Transport
-
Cell Compartmentation
-
Cell Nucleus / metabolism*
-
Cellular Apoptosis Susceptibility Protein
-
Fungal Proteins / genetics
-
Fungal Proteins / isolation & purification
-
Fungal Proteins / metabolism*
-
Green Fluorescent Proteins
-
Karyopherins
-
Luminescent Proteins / genetics
-
Luminescent Proteins / isolation & purification
-
Nuclear Envelope / chemistry
-
Nuclear Proteins / metabolism*
-
Nucleocytoplasmic Transport Proteins
-
Precipitin Tests
-
Protein Binding
-
Proteins
-
Recombinant Fusion Proteins / isolation & purification
-
Recombinant Fusion Proteins / metabolism
-
Saccharomyces cerevisiae
-
Saccharomyces cerevisiae Proteins*
-
alpha Karyopherins
Substances
-
CSE1 protein, S cerevisiae
-
Cellular Apoptosis Susceptibility Protein
-
Fungal Proteins
-
Karyopherins
-
Luminescent Proteins
-
Nuclear Proteins
-
Nucleocytoplasmic Transport Proteins
-
Proteins
-
Recombinant Fusion Proteins
-
Saccharomyces cerevisiae Proteins
-
alpha Karyopherins
-
Green Fluorescent Proteins