Cancer Research UK Paterson Institute for Cancer Research, University of Manchester, UK.
Curr Biol. 2009 Dec 1;19(22):1943-9. doi: 10.1016/j.cub.2009.09.062. Epub 2009 Nov 12.
Eukaryotic cells contain multiple versions of the E3 ubiquitin ligase known as the SCF (Skp1/cullin/F box), each of which is distinguished by a different F box protein that uses a domain at the carboxyl terminus to recognize substrates [1, 2]. The F box protein Dia2 is an important determinant of genome stability in budding yeast [3-5], but its mode of action is poorly understood. Here we show that SCF(Dia2) associates with the replisome progression complex (RPC) that assembles around the MCM2-7 helicase at DNA replication forks [6]. This interaction requires the RPC components Mrc1 and Ctf4, both of which associate with a tetratricopeptide repeat (TPR) domain located at the amino terminus of Dia2. Our data indicate that the TPR domain of Dia2 tethers SCF(Dia2) to the RPC, probably increasing the local concentration of the ligase at DNA replication forks. This regulation becomes important in cells that accumulate stalled DNA replication forks at protein-DNA barriers, perhaps aiding the interaction of SCF(Dia2) with key substrates. Our findings suggest that the amino-terminal domains of other F box proteins might also play an analogous regulatory role, controlling the localization of the cognate SCF complexes.
真核细胞中存在多种 E3 泛素连接酶（E3 ubiquitin ligase），即 SCF（Skp1/cullin/F -box）复合物，每种复合物都由不同的 F -box 蛋白区分，该蛋白羧基末端的一个结构域可识别底物[1,2]。F -box 蛋白 Dia2 是芽殖酵母基因组稳定性的一个重要决定因素[3-5]，但其作用机制尚不清楚。本文中，我们发现 SCF(Dia2)与复制体前进复合物（replicisome progression complex，RPC）相关，该复合物在 DNA 复制叉处围绕 MCM2-7 解旋酶组装[6]。这种相互作用需要 RPC 成分 Mrc1 和 Ctf4，二者均与位于 Dia2 氨基端的四肽重复（tetratricopeptide repeat，TPR）结构域结合。数据表明，Dia2 的 TPR 结构域将 SCF(Dia2)连接到 RPC 上，可能增加了 DNA 复制叉处 ligase 的局部浓度。在蛋白质-DNA 障碍处积累停滞的 DNA 复制叉的细胞中，这种调控变得尤为重要，这可能有助于 SCF(Dia2)与关键底物的相互作用。研究结果表明，其他 F -box 蛋白的氨基端结构域可能也具有类似的调节作用，控制着相应的 SCF 复合物的定位。
