Abstract
Nucleation of branched actin filaments by the Arp2/3 complex is a conserved process in eukaryotic cells, yet the source of unbranched actin filaments has remained obscure. In yeast, formins stimulate assembly of actin cables independently of Arp2/3. Here, the conserved core of formin homology domains 1 and 2 of Bni1p (Bni1pFH1FH2) was found to nucleate unbranched actin filaments in vitro. Bni1pFH2 provided the minimal region sufficient for nucleation. Unique among actin nucleators, Bni1pFH1FH2 remained associated with the growing barbed ends of filaments. This combination of properties suggests a direct role for formins in regulating nucleation and polarization of unbranched filamentous actin 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 Cytoskeleton / metabolism*
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Actin Cytoskeleton / ultrastructure
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Actins / metabolism*
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Cytochalasin B / pharmacology
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Fungal Proteins / chemistry*
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Fungal Proteins / metabolism*
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Microfilament Proteins*
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Microscopy, Electron
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Protein Structure, Tertiary
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Saccharomyces cerevisiae / metabolism*
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Saccharomyces cerevisiae / ultrastructure
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Saccharomyces cerevisiae Proteins / chemistry
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Saccharomyces cerevisiae Proteins / metabolism
Substances
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Actins
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Bni1 protein, S cerevisiae
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Fungal Proteins
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Microfilament Proteins
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Recombinant Fusion Proteins
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Saccharomyces cerevisiae Proteins
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Cytochalasin B