Interaction of Bnr1p with a Novel Src Homology 3 Domain-containing Hof1p

doi:10.1074/jbc.273.43.28341

Interaction of Bnr1p with a Novel Src Homology 3 Domain-containing Hof1p

IMPLICATION IN CYTOKINESIS IN *SACCHAROMYCES CEREVISIAE**

From the Department of Molecular Biology and Biochemistry, Osaka University Medical School, Suita 565-0871, Osaka, Japan

Abstract

Proteins containing the formin homology (FH) domains FH1 and FH2 are involved in cytokinesis or establishment of cell polarity in a variety of organisms. We have shown that the FH proteins Bni1p and Bnr1p are potential targets of the Rho family small GTP-binding proteins and bind to an actin-binding protein, profilin, at their proline-rich FH1 domains to regulate reorganization of the actin cytoskeleton in the yeast Saccharomyces cerevisiae. We found here that a novel Src homology 3 (SH3) domain-containing protein, encoded by YMR032w, interacted with Bnr1p in a GTP-Rho4p-dependent manner through the FH1 domain of Bnr1p and the SH3 domain of Ymr032wp. Ymr032wp weakly bound to Bni1p. Ymr032wp was homologous to cdc15p, which is involved in cytokinesis inSchizosaccharomyces pombe, and we named this geneHOF1 (homolog of cdc 15). Both Bnr1p and Hof1p were localized at the bud neck, and both the bnr1 andhof1 mutations showed synthetic lethal interactions with the bni1 mutation. The hof1 mutant cells showed phenotypes similar to those of the septin mutants, indicating thatHOF1 is involved in cytokinesis. These results indicate that Bnr1p directly interacts with Hof1p as well as with profilin to regulate cytoskeletal functions in S. cerevisiae.

Footnotes

↵* This investigation was supported by grants-in-aid for Scientific Research and for Cancer Research from the Ministry of Education, Science, Sports, and Culture of Japan (1997), by grants-in-aid for Abnormalities in Hormone Receptor Mechanisms and for Aging and Health from the Ministry of Health and Welfare of Japan (1997), and by a grant from the Human Frontier Science Program (1997).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
↵‡ Present address: Tsukuba Research Laboratories, Eisai Co., Ltd., 5-1-3, Tokodai, Tsukuba, Ibaraki 300-2635, Japan.
↵§ Present address: Second Department of Surgery, Osaka University Medical School, Suita 565-0871, Osaka, Japan.
↵¶ To whom correspondence should be addressed. Tel.: 81-6-879-3410; Fax: 81-6-879-3419; E-mail:ytakai{at}molbio.med.osaka-u.ac.jp.
↵2 T. Kamei, K. Tanaka, T. Hihara, M. Umikawa, H. Imamura, M. Kikyo, K. Ozaki, and Y. Takai, unpublished results.
Abbreviations:

FH

formin homology

SH3

Src homology 3

DBD_LexA

DNA-binding domain of LexA

AD_GAL4

transcriptional activation domain of GAL4

MBP

maltose-binding protein

GST

glutathione S-transferase

kbp

kilobase pair(s).
- Received April 28, 1998.
- Revision received August 4, 1998.
The American Society for Biochemistry and Molecular Biology, Inc.