Acetylation regulates tropomyosin function in the fission yeast Schizosaccharomyces pombe.
Tropomyosin is an evolutionarily conserved alpha-helical coiled-coil protein that promotes and maintains actin filaments. In yeast, Tropomyosin-stabilised filaments are used by molecular motors to transport cargoes or to generate motile forces by altering the dynamics of filament growth and shrinkage. The Schizosaccharomyces pombe tropomyosin Cdc8 localises to the cytokinetic actomyosin ring during mitosis and is absolutely required for its formation and function. We show that Cdc8 associates with actin filaments throughout the cell cycle and is subjected to post-translational modification that does not vary with cell cycle progression. At any given point in the cell cycle 80% of Cdc8 molecules are acetylated, which significantly enhances their affinity for actin. Reconstructions of electron microscopic images of actin-Cdc8 filaments establish that the majority of Cdc8 strands sit in the 'closed' position on actin filaments, suggesting a role in the regulation of myosin binding. We show that Cdc8 regulates the equilibrium binding of myosin to actin without affecting the rate of myosin binding. Unacetylated Cdc8 isoforms bind actin, but have a reduced ability to regulate myosin binding to actin. We conclude that although acetylation of Cdc8 is not essential, it provides a regulatory mechanism for modulating actin filament integrity and myosin function.
Skoumpla
Kalomoira
K
Cell and Developmental Biology Group, Department of Biosciences, University of Kent at Canterbury, Canterbury, CT2 7NJ, UK.
Coulton
Arthur T
AT
Lehman
William
W
Geeves
Michael A
MA
Mulvihill
Daniel P
DP
D000107:Acetylation; D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D000199:Actins / Q000378:metabolism; D000595:Amino Acid Sequence; D015153:Blotting, Western; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D021621:Imaging, Three-Dimensional; D007399:Interphase / Q000502:physiology; D007700:Kinetics; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009218:Myosins / Q000378:metabolism; D011485:Protein Binding; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D014335:Tropomyosin / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
D000199:Actins; C410737:Cdc8 protein, S pombe; D018797:Cell Cycle Proteins; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; C490772:TPM1 protein, S cerevisiae; D014335:Tropomyosin; D049452:Green Fluorescent Proteins; D009218:Myosins