Coupling of septins to the axial landmark by Bud4 in budding yeast
Coupling of septins to the axial landmark by Bud4 in budding yeast
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DOI：
10.1242/jcs.118521
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发表时间：
2013-03-01
影响因子：
4
通讯作者：
Park, Hay-Oak
中科院分区：
文献类型：
--
作者：
Kang, Pil Jung;Hood-DeGrenier, Jennifer K.;Park, Hay-Oak
芽殖酵母酿酒酵母的细胞选择一个位点，以特定的模式极化生长，这取决于它们的细胞类型。单倍体a和a细胞以轴向出芽模式出芽，这需要包括Bud4蛋白的地标的组装。为了了解如何建立一个轴芽网站，我们进行了Bud4的结构功能分析。Bud4含有DUF1709（domain of unknown functionality），其类似于anillin同源结构域的一部分，并且在其C末端附近含有推定的Pleckstrin同源（PH）结构域。虽然它的定位依赖于septins，一个保守的GTP结合蛋白家族，Bud4是细胞分裂过程中septin环稳定遗传所必需的。虽然一些苯胺直接与septins相互作用，我们发现DUF1709和PH结构域都不是将Bud4靶向母芽颈所必需的。相反，该C-末端区域对于Bud4与Bud3和轴向标志的其他组分的关联至关重要。值得注意的是，septins与缺乏这些C-末端结构域的Bud4突变蛋白共定位，在胞质分裂期间和之后形成弧形或单环而不是双环。有趣的是，Bud4的过表达还诱导形成与septins相关的额外Bud4环和弧。一系列的bud4截断突变体的分析表明，至少有两个结构域的中心区域发挥冗余的作用，在针对Bud4的母芽颈，因此可能与septins相互作用。综上所述，这些结果表明Bud4作为一个平台，将分隔蛋白连接到轴向标志。
Cells of the budding yeast Saccharomyces cerevisiae select a site for polarized growth in a specific pattern that depends on their cell type. Haploid a and a cells bud in the axial budding pattern, which requires assembly of a landmark that includes the Bud4 protein. To understand how an axial bud site is established, we performed a structure-function analysis of Bud4. Bud4 contains DUF1709 (domain of unknown function), which is similar to a part of the anillin-homology domain, and a putative Pleckstrin homology (PH) domain near to its C terminus. Although its localization depends on septins, a conserved family of GTP-binding proteins, Bud4 is necessary for the stable inheritance of septin rings during cell division. Although some anillins interact directly with septins, we find that neither DUF1709 nor the PH domain is necessary for targeting Bud4 to the mother-bud neck. Instead, this C-terminal region is crucial for association of Bud4 with Bud3 and other components of the axial landmark. Remarkably, septins colocalize with Bud4 mutant proteins that lack these C-terminal domains, forming an arc or a single ring instead of a double ring during and after cytokinesis. Interestingly, overexpression of Bud4 also induces formation of extra Bud4 rings and arcs that are associated with septins. Analyses of a series of bud4 truncation mutants suggest that at least two domains in the central region play a redundant role in targeting Bud4 to the mother-bud neck and are thus likely to interact with septins. Taken together, these results indicate that Bud4 functions as a platform that links septins to the axial landmark.