Sro7p, a Saccharomyces cerevisiae counterpart of the tumor suppressor l(2)gl protein, is related to myosins in function.
Yeast SRO7 was identified as a multicopy suppressor of a defect in Rho3p, a small GTPase that maintains cell polarity. Sro7p and Sro77p, a homologue of Sro7p, possess domains homologous to the protein that are encoded by the Drosophila tumor suppressor gene lethal (2) giant larvae [l(2)gl]. sro7Delta sro77Delta mutants showed a partial defect of organization of the polarized actin cytoskeleton and a cold-sensitive growth phenotype. A human counterpart of l(2)gl could suppress the sro7Delta sro77Delta defect. Similar to the l(2)gl protein, Sro7p formed a complex with Myo1p, a type II myosin. These results indicate that Sro7p and Sro77p are the yeast counterparts of the l(2)gl protein. Our genetic analysis revealed that deletion of SRO7 and SRO77 showed reciprocal suppression with deletion of MYO1 (i.e., the sro7Delta sro77Delta defect was suppressed by myo1Delta and vice versa). In addition, SRO7 showed genetic interactions with MYO2, encoding an essential type V myosin: Overexpression of SRO7 suppressed a defect in MYO2 and, conversely, overexpression of MYO2 suppressed the cold-sensitive phenotype of sro7Delta sro77Delta mutants. These results indicate that Sro7 function is closely related to both Myo1p and Myo2p. We propose a model in which Sro7 function is involved in the targeting of the myosin proteins to their intrinsic pathways.
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Tokyo 113, Japan.
M
M
Kagami
A
A
Toh-e
Y
Y
Matsui
D000199:Actins / Q000502:physiology; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology; D016764:Cell Polarity / Q000235:genetics / Q000502:physiology; D002874:Chromosome Mapping; D003599:Cytoskeleton / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D029721:Drosophila Proteins; D005656:Fungal Proteins / Q000235:genetics* / Q000502:physiology; D005800:Genes, Fungal; D006801:Humans; D019476:Insect Proteins / Q000235:genetics*; D008954:Models, Biological; D008969:Molecular Sequence Data; D018995:Myosin Heavy Chains / Q000235:genetics / Q000502:physiology; D024461:Myosin Type I; D024462:Myosin Type II; D024701:Myosin Type V; D010641:Phenotype; D016133:Polymerase Chain Reaction; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D025521:Tumor Suppressor Proteins
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D017931:DNA Primers; D029721:Drosophila Proteins; D005656:Fungal Proteins; D019476:Insect Proteins; C112936:MYO1 protein, S cerevisiae; C062291:MYO1A protein, human; C077512:MYO2 protein, S cerevisiae; C434211:MYO2 protein, S pombe; C116430:SRO7 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D025521:Tumor Suppressor Proteins; C081435:l(2)gl protein, Drosophila; C491828:myo1 protein, S pombe; D024461:Myosin Type I; D024462:Myosin Type II; D024701:Myosin Type V; D018995:Myosin Heavy Chains