Evangelista Marie, Zigmond Sally, Boone Charles
Department of Biology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
J Cell Sci. 2003 Jul 1;116(Pt 13):2603-11. doi: 10.1242/jcs.00611.
Eukaryotic cells require filamentous actin to maintain their shape and for movement, growth and replication. New actin filaments are formed by the cutting of existing filaments or de novo through the action of specialized nucleators. The most highly characterized nucleator is the Arp2/3 complex, which nucleates the branched actin networks in the lamellae of migrating cells. Recently, Bni1p, which is a member of the formin family of proteins, has been shown to nucleate actin filaments in vitro. Formins are implicated in the formation of actin cables in yeast, stress fibers in tissue culture cells and cytokinesis in many cell types. Formins contain two highly conserved formin-homology domains, FH1 and FH2. The Bni1p FH2 domain is sufficient to mediate nucleation. The Bni1p FH1 domain binds profilin, an actin-monomer-binding protein that delivers actin to the growing barbed end of filaments. The Bni1p FH1-profilin interaction enhances nucleation. Formins participate in a number of signaling pathways that control the assembly of specific actin structures and bind the barbed end of actin filaments, thereby providing a cytoskeletal basis for the establishment of cell polarity.
真核细胞需要丝状肌动蛋白来维持其形状，并用于运动、生长和复制。新的肌动蛋白丝通过切割现有丝或通过专门的成核剂从头合成形成。特征最明显的成核剂是Arp2/3复合体，它在迁移细胞的片状伪足中形成分支状肌动蛋白网络。最近，作为formin家族蛋白质成员之一的Bni1p已被证明在体外能使肌动蛋白丝成核。Formin参与酵母中肌动蛋白电缆、组织培养细胞中的应力纤维以及许多细胞类型中的胞质分裂的形成。Formin包含两个高度保守的formin同源结构域，即FH1和FH2。Bni1p的FH2结构域足以介导成核。Bni1p的FH1结构域结合原肌球蛋白，原肌球蛋白是一种肌动蛋白单体结合蛋白，它将肌动蛋白输送到丝的生长中的带刺末端。Bni1p的FH1-原肌球蛋白相互作用增强成核作用。Formin参与许多控制特定肌动蛋白结构组装的信号通路，并结合肌动蛋白丝的带刺末端，从而为细胞极性的建立提供细胞骨架基础。
