Abstract
Formins are required for cell polarization and cytokinesis, but do not have a defined biochemical activity. In Saccharomyces cerevisiae, formins and the actin-monomer-binding protein profilin are specifically required to assemble linear actin structures called 'actin cables'. These structures seem to be assembled independently of the Arp2/3 complex, the only well characterized cellular mediator of actin nucleation. Here, an activated yeast formin was purified and found to promote the nucleation of actin filaments in vitro. Formin-dependent actin nucleation was stimulated by profilin. Thus, formin and profilin mediate actin nucleation by an Arp2/3-independent mechanism. These findings suggest that distinct actin nucleation mechanisms may underlie the assembly of different actin cytoskeletal structures.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Actin-Related Protein 2
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Actin-Related Protein 3
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Actins / chemistry
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Actins / genetics
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Actins / metabolism*
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Biopolymers / chemistry
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Biopolymers / genetics
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Biopolymers / metabolism
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Cell Cycle Proteins / genetics
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Cell Cycle Proteins / metabolism*
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Cytoskeletal Proteins*
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Cytoskeleton / metabolism
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Fungal Proteins / genetics
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Fungal Proteins / metabolism*
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Microfilament Proteins*
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Profilins
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Protein Binding
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Saccharomyces cerevisiae / cytology
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Saccharomyces cerevisiae / genetics
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Saccharomyces cerevisiae / metabolism
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Saccharomyces cerevisiae Proteins / genetics
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Saccharomyces cerevisiae Proteins / metabolism*
Substances
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ARP3 protein, S cerevisiae
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Actin-Related Protein 2
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Actin-Related Protein 3
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Actins
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Biopolymers
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Bni1 protein, S cerevisiae
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CDC3 protein, S cerevisiae
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Cell Cycle Proteins
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Cytoskeletal Proteins
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Fungal Proteins
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Microfilament Proteins
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Profilins
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Saccharomyces cerevisiae Proteins