The yeast MYO1 gene encoding a myosin-like protein required for cell division.

Abstract

A yeast gene MYO1 that contains regions of substantial sequence homology with the nematode muscle myosin gene (unc54) has been isolated and sequenced. Although the disruption of MYO1 is not lethal, it leads to aberrant nuclear migration and cytokinesis. The 200‐kd myosin heavy chain‐like protein, the product of MYO1, cross‐reacts with anti‐nematode myosin heavy chain IgG and is present in wild‐type strains but not in strains carrying the disrupted gene. Instead, a truncated polypeptide with a molecular mass of 120 kd can be detected in some myo1 mutants.

Myosin-II Tails Confer Unique Functions inSchizosaccharomyces pombe: Characterization of a Novel Myosin-II Tail

“…Myo1p is the only budding yeast myosin-II, and it is not essential. However, deletion of the S. cerevisiae myosin-II gene leads to defects in cytokinesis (Watts et al, 1987), reminiscent of the ⌬myp2 phenotype in S. pombe (this work; Bezanilla et al, 1997). Cell division in S. cerevisiae requires formation of a bud and directed transport of intracellular components into the bud.…”

“…Of the unicellular organisms such as Acanthamoeba, Dictyostelium, and Saccharomyces cerevisiae, where myosin-II has been cloned and or biochemically isolated (Watts et al, 1987;Sellers et al, 1996), Schizosaccharomyces pombe is unique in that it has two myosin-IIs, Myo2p May et al, 1997) and Myp2p (Bezanilla et al, 1997;Motegi et al, 1997). Their functions have been deduced from genetic studies.…”

Advances in Cytokinesis Research. Cytokinesis in Budding Yeast: The Relationship between Actomyosin Ring Function and Septum Formation.

“…Second, the contraction of the actomyosin ring in budding yeast must be coordinated temporally and spatially with septum formation, whereas, in animal cells, a septum does not exist. Third, unlike in fission yeast and animal cells, the actomyosin ring is not essential for cell viability and cytokinesis in budding yeast (Bi et al, 1998;Rodriguez and Paterson, 1990;Watts et al, 1987).…”

“…Thus, the order of protein assembly at the bud neck is as follows: septins Myo1p F-actin. Deletion of MYO1 is not lethal, but causes a delay in cytokinesis and cell separation (Bi et al, 1998;Rodriguez and Paterson, 1990;Watts et al, 1987).…”

“…Deletion of MYO1 eliminates the actomyosin ring, yet the myo1 null cells form colonies with cells in short chains, indicating that the actomyosin ring is not essential but is required for efficient cytokinesis (Bi et al, 1998;Rodriguez and Paterson, 1990;Watts et al, 1987). Electron microscopic studies showed that myo1 null cells formed abnormally thick, irregularly shaped septa (Rodriguez and Paterson, 1990), suggesting that the actomyosin ring plays a role in septum maturation and/or cell separation.…”