Lee W L, Bezanilla M, Pollard T D
Graduate Program in Biochemistry, Cellular and Molecular Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
J Cell Biol. 2000 Nov 13;151(4):789-800. doi: 10.1083/jcb.151.4.789.
Fission yeast myo1(+) encodes a myosin-I with all three tail homology domains (TH1, 2, 3) found in typical long-tailed myosin-Is. Myo1p tail also contains a COOH-terminal acidic region similar to the A-domain of WASp/Scar proteins and other fungal myosin-Is. Our analysis shows that Myo1p and Wsp1p, the fission yeast WASp-like protein, share functions and cooperate in controlling actin assembly. First, Myo1p localizes to cortical patches enriched at tips of growing cells and at sites of cell division. Myo1p patches partially colocalize with actin patches and are dependent on an intact actin cytoskeleton. Second, although deletion of myo1(+) is not lethal, Deltamyo1 cells have actin cytoskeletal defects, including loss of polarized cell growth, delocalized actin patches, and mating defects. Third, additional disruption of wsp1(+) is synthetically lethal, suggesting that these genes may share functions. In mapping the domains of Myo1p tail that share function with Wsp1p, we discovered that a Myo1p construct with just the head and TH1 domains is sufficient for cortical localization and to rescue all Deltamyo1 defects. However, it fails to rescue the Deltamyo1 Deltawsp1 lethality. Additional tail domains, TH2 and TH3, are required to complement the double mutant. Fourth, we show that a recombinant Myo1p tail binds to Arp2/3 complex and activates its actin nucleation activity.
裂殖酵母myo1(+)编码一种肌球蛋白-I，其具有典型长尾肌球蛋白-I中发现的所有三个尾部同源结构域（TH1、2、3）。Myo1p尾部还包含一个COOH末端酸性区域，类似于WASp/Scar蛋白的A结构域和其他真菌肌球蛋白-I。我们的分析表明，Myo1p和裂殖酵母中类WASp蛋白Wsp1p在控制肌动蛋白组装方面具有共同功能并相互协作。首先，Myo1p定位于生长细胞顶端和细胞分裂部位富集的皮质斑。Myo1p斑与肌动蛋白斑部分共定位，并且依赖于完整的肌动蛋白细胞骨架。其次，虽然缺失myo1(+)并不致命，但Δmyo1细胞存在肌动蛋白细胞骨架缺陷，包括极性细胞生长丧失、肌动蛋白斑定位异常以及交配缺陷。第三，额外破坏wsp1(+)具有合成致死性，表明这些基因可能具有共同功能。在绘制与Wsp1p具有共同功能的Myo1p尾部结构域时，我们发现仅具有头部和TH1结构域的Myo1p构建体足以进行皮质定位并挽救所有Δmyo1缺陷。然而，它无法挽救Δmyo1Δwsp1的致死性。需要额外的尾部结构域TH2和TH3来补充双突变体。第四，我们表明重组Myo1p尾部与Arp2/3复合物结合并激活其肌动蛋白成核活性。
