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Vol. 14, Issue 6, 2237-2249, June 2003

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She4p/Dim1p Interacts with the Motor Domain of Unconventional Myosins in the Budding Yeast, Saccharomyces cerevisiae

Hirofumi Toi ^* , Konomi Fujimura-Kamada ^*, Kenji Irie , Yoshimi Takai , Satoru Todo , and Kazuma Tanaka ^* 

^* Division of Molecular Interaction, Institute for Genetic Medicine, Hokkaido University Graduate School of Medicine, Hokkaido 060-0815, Japan; Department of Molecular Biology and Biochemistry, Osaka University Graduate School of Medicine, Osaka 565-0871, Japan; and Department of General Surgery, Hokkaido University Graduate School of Medicine, Hokkaido 060-8638, Japan

Submitted September 27, 2002; Revised January 10, 2003; Accepted January 30, 2003
Monitoring Editor: David Drubin

She4p/Dim1p, a member of the UNC-45/CRO1/She4p (UCS) domain-containing protein family, is required for endocytosis, polarization of actin cytoskeleton, and polarization of ASH1 mRNA in Saccharomyces cerevisiae. We show herein that She4p/Dim1p is involved in endocytosis and actin polarization through interactions with the type I myosins Myo3p and Myo5p. Two-hybrid and biochemical experiments showed that She4p/Dim1p interacts with the motor domain of Myo3/5p through its UCS domain. She4p/Dim1p was required for Myo5p localization to cortical patch-like structures. Using random mutagenesis of the motor region of MYO5, we identified four independent dominant point mutations that suppress the temperature-sensitive growth phenotype of the she4/dim1 null mutant. All of the amino acid substitutions caused by these mutations, V164I, N168I, N209S, and K377M, could suppress the defects of endocytosis and actin polarization of the she4/dim1 mutant as well. She4p/Dim1p also showed two-hybrid interactions with the motor domain of a type II myosin Myo1p and type V myosins Myo2p and Myo4p, and was required for proper localization of Myo4p, which regulates polarization of ASH1 mRNA. Our results suggest that She4p/Dim1p is required for structural integrity or regulation of the motor domain of unconventional myosins.

Corresponding author. E-mail address: k-tanaka{at}med.hokudai.ac.jp.