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Cooperation of two actin‐binding proteins, cofilin and Aip1, in Saccharomyces cerevisiae
Author(s) -
Iida Kazuko,
Yahara Ichiro
Publication year - 1999
Publication title -
genes to cells
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.912
H-Index - 115
eISSN - 1365-2443
pISSN - 1356-9597
DOI - 10.1046/j.1365-2443.1999.00235.x
Subject(s) - cofilin , biology , saccharomyces cerevisiae , actin binding protein , actin , mutant , microbiology and biotechnology , actin cytoskeleton , gene , cytoskeleton , biochemistry , cell
Background Cofilin is a low‐molecular weight actin‐modulating protein, and is structurally and functionally conserved among eukaryotes. Cofilin is encoded by COF1 in Saccharomyces cerevisiae , and is essential for cell viability. Cofilin binds to and severs actin filaments in vitro , and also enhances their depolymerization. A partner protein that cooperates with cofilin in vivo has not been identified. Results When COF1 was over‐expressed in yeast cells under the GAL1 promoter in a medium containing galactose as a sole carbon source, the cells did not survive. These results indicate that cells can grow only when the expression of cofilin is appropriately regulated. Several temperature sensitive (ts‐) mutants were independently created by the random mutagenesis of COF1 with hydroxylamine. Mutated amino acids in ts‐mutants were mapped in the sequences that were presumed to be involved in actin binding. A gene on a multicopy plasmid which suppresses the ts‐phenotype of cof1‐101 , a typical ts‐cofilin mutant, was isolated. The suppressor gene, SCF1 , was found to be identical to AIP1 , a gene encoding an actin‐interacting protein. Although SCF1 / AIP1 is not essential for cell viability, a combination of cof1‐101 and Δscf1/aip1 is synthetic lethal. Immunofluorescence staining of a wild‐type strain using anti‐Aip1 antibodies revealed that Aip1 was distributed in cortical actin patches where cofilin was also co‐localized. Thick and long fibres stained with anti‐cofilin antibody were detected in Δscf1/aip1 cells, but not in SCF1/AIP1 cells. Conclusions These results suggest the cooperative modulation of the actin cytoskeleton by cofilin and Aip1.