Identification and functional analysis of the gene for type I myosin in fission yeast.
BACKGROUND
Type I myosin is highly conserved among eukaryotes, and apparently plays important roles in a number of cellular processes. In the budding yeast, two myosin I species have been identified and their role in F-actin assembly has been inferred.


RESULTS
We cloned the fission yeast myo1 gene, which apparently encoded a myosin I protein. Disruption of myo1 was not lethal, but it caused growth retardation at high and low temperatures, sensitivity to a high concentration of KCl, and aberrance in cell morphology associated with an abnormal distribution of F-actin patches. An abnormal deposition of cell wall materials was also seen. Homothallic myo1Delta cells could mate, but heterothallic myo1Delta cells were poor in conjugation. Myo1p was necessary for the encapsulation of spores. The tail domain of Myo1p was pivotal for its function. Calmodulin could bind to Myo1p through the IQ domain at the neck.


CONCLUSIONS
Myo1p appears to control the redistribution of F-actin patches during the cell cycle. Loss of Myo1p function is likely to slow down the actin assembly/disassembly process, which results in a failure of the actin cycle to catch up with other events in both the mitotic and meiotic cell cycles, including extension of the conjugation tubes.
Toya
M
M
Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan.
Motegi
F
F
Nakano
K
K
Mabuchi
I
I
Yamamoto
M
M
D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution / Q000235:genetics; D048429:Cell Size / Q000235:genetics; D002473:Cell Wall / Q000235:genetics; D003001:Cloning, Molecular; D003080:Cold Temperature; D005656:Fungal Proteins / Q000378:metabolism; D017353:Gene Deletion; D018390:Gene Targeting; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009218:Myosins / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D013172:Spores, Fungal / Q000235:genetics / Q000502:physiology; D013696:Temperature
D000199:Actins; C080581:CAM1 protein, S cerevisiae; D005656:Fungal Proteins; D020648:Peptide Elongation Factor 1; D010445:Peptide Elongation Factors; D029701:Saccharomyces cerevisiae Proteins; D009218:Myosins