The SH3 domain-containing protein Bem1p is needed for normal bud emergence and mating projection formation, two processes that require asymmetric reorganizations of the cortical cytoskeleton in Saccharomyces cerevisiae. To identify proteins that functionally and/or physically interact with Bem1p, we screened for mutations that display synthetic lethality with a mutant allele of the BEM1 gene and for genes whose products display two-hybrid interactions with the Bem1 protein. CDC24, which is required for bud emergence and encodes a GEF (guanine-nucleotide exchange factor) for the essential Rho-type GTPase Cdc42p, was identified during both screens. The COOH-terminal 75 amino acids of Cdc24p, outside of the GEF domain, can interact with a portion of Bem1p that lacks both SH3 domains. Bacterially expressed Cdc24p and Bem1p bind to each other in vitro, indicating that no other yeast proteins are required for this interaction. The most frequently identified gene that arose from the bem1 synthetic-lethal screen was the bud-emergence gene BEM2 (Bender and Pringle. 1991. Mol. Cell Biol. 11:1295-1395), which is allelic with IPL2 (increase in ploidy; Chan and Botstein, 1993. Genetics. 135:677-691). Here we show that Bem2p contains a GAP (GTPase-activating protein) domain for Rho-type GTPases, and that this portion of Bem2p can stimulate in vitro the GTPase activity of Rho1p, a second essential yeast Rho-type GTPase. Cells deleted for BEM2 become large and multinucleate. These and other genetic, two-hybrid, biochemical, and phenotypic data suggest that multiple Rho-type GTPases control the reorganization of the cortical cytoskeleton in yeast and that the functions of these GTPases are tightly coupled. Also, these findings raise the possibility that Bem1p may regulate or be a target of action of one or more of these GTPases.
Skip Nav Destination
Article navigation
1 December 1994
Article|
December 01 1994
Interactions between the bud emergence proteins Bem1p and Bem2p and Rho-type GTPases in yeast.
J Peterson,
J Peterson
Department of Biology, Indiana University, Bloomington 47405.
Search for other works by this author on:
Y Zheng,
Y Zheng
Department of Biology, Indiana University, Bloomington 47405.
Search for other works by this author on:
L Bender,
L Bender
Department of Biology, Indiana University, Bloomington 47405.
Search for other works by this author on:
A Myers,
A Myers
Department of Biology, Indiana University, Bloomington 47405.
Search for other works by this author on:
R Cerione,
R Cerione
Department of Biology, Indiana University, Bloomington 47405.
Search for other works by this author on:
A Bender
A Bender
Department of Biology, Indiana University, Bloomington 47405.
Search for other works by this author on:
J Peterson
Department of Biology, Indiana University, Bloomington 47405.
Y Zheng
Department of Biology, Indiana University, Bloomington 47405.
L Bender
Department of Biology, Indiana University, Bloomington 47405.
A Myers
Department of Biology, Indiana University, Bloomington 47405.
R Cerione
Department of Biology, Indiana University, Bloomington 47405.
A Bender
Department of Biology, Indiana University, Bloomington 47405.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1994) 127 (5): 1395–1406.
Citation
J Peterson, Y Zheng, L Bender, A Myers, R Cerione, A Bender; Interactions between the bud emergence proteins Bem1p and Bem2p and Rho-type GTPases in yeast.. J Cell Biol 1 December 1994; 127 (5): 1395–1406. doi: https://doi.org/10.1083/jcb.127.5.1395
Download citation file:
Sign in
Don't already have an account? Register
Client Account
You could not be signed in. Please check your email address / username and password and try again.
Could not validate captcha. Please try again.
Sign in via your Institution
Sign in via your InstitutionSuggested Content
Email alerts
Advertisement
Advertisement