Interactions among Rax1p, Rax2p, marking cortical sites for bipolar yeast
Interactions among Rax1p, Rax2p, marking cortical sites for bipolar yeast
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DOI：
10.1091/mbc.e04-07-0600
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发表时间：
2004-11-01
影响因子：
3.3
通讯作者：
Park, HO
中科院分区：
文献类型：
--
作者：
Kang, PJ;Angerman, E;Park, HO
在萌芽酵母中，芽位的选择决定了细胞的极化生长和最终定向分裂的轴线。芽位根据细胞类型以特定的模式进行选择。这些模式似乎取决于细胞皮质中不同类型的标记蛋白；特别是，二倍体细胞的两极出芽依赖于出生疤痕远端和近端的持久标志，这些标志分别涉及蛋白质Bud8p和Bud9p。Rax1p和Rax2p似乎也在双极发芽中特异发挥功能，我们在这里报告了这些蛋白的进一步特征以及它们与Bud8p和Bud9p的相互作用。Rax1p和Rax2p似乎都是完整的膜蛋白。尽管常用的程序预测了Rax2p的不同拓扑结构，但糖基化研究表明它具有I型取向，其N末端结构域位于胞外空间。对rax1和rax2突变发芽模式的分析表明，这两种蛋白都参与了在子细胞的远端和近端以及母细胞上以前使用的分裂部位附近的芽位选择。与此一致的是，GFP标记的Rax1p和Rax2p在母细胞和子细胞的远端极和分裂部位都被观察到；分裂部位的定位在多个细胞周期中持续存在。Rax1p和Rax2p的定位是相互依赖的，生化研究表明这些蛋白可以从酵母中获得。Bud8p和Bud9p也可以与Rax1p共生，定位研究为相互作用提供了进一步的证据。Rax1p和Rax2p在芽尖和远端的定位依赖于Bud8p，而Bud8p的正常定位部分依赖于Rax1p和Rax2p。虽然Rax1p和Rax2p在分裂位点的定位似乎不依赖于Bud9p，但Bud9p的正常定位在很大程度上或完全依赖于Rax1p和Rax2p。综上所述，结果表明，Rax1p和Rax2p在建立和/或维持双极萌发的皮层标志物方面相互作用密切，并与Bud8p和Bud9p相互作用。
In the budding yeast Saccharomyces cerevisiae, selection of the bud site determines the axis of polarized cell growth and eventual oriented cell division. Bud sites are selected in specific patterns depending on cell type. These patterns appear to depend on distinct types of marker proteins in the cell cortex; in particular, the bipolar budding of diploid cells depends on persistent landmarks at the birth-scar-distal and -proximal poles that involve the proteins Bud8p and Bud9p, respectively. Rax1p and Rax2p also appear to function specifically in bipolar budding, and we report here a further characterization of these proteins and of their interactions with Bud8p and Bud9p. Rax1p and Rax2p both appear to be integral membrane proteins. Although commonly used programs predict different topologies for Rax2p, glycosylation studies indicate that it has a type I orientation, with its long N-terminal domain in the extracytoplasmic space. Analysis of rax1 and rax2 mutant budding patterns indicates that both proteins are involved in selecting bud sites at both the distal and proximal poles of daughter cells as well as near previously used division sites on mother cells. Consistent with this, GFP-tagged Rax1p and Rax2p were both observed at the distal pole as well as at the division site on both mother and daughter cells; localization to the division sites was persistent through multiple cell cycles. Localization of Rax1p and Rax2p was interdependent, and biochemical studies showed that these proteins could be copurified from yeast. Bud8p and Bud9p could also be copurified with Rax1p, and localization studies provided further evidence of interactions. Localization of Rax1p and Rax2p to the bud tip and distal pole depended on Bud8p, and normal localization of Bud8p was partially dependent on Rax1p and Rax2p. Although localization of Rax1p and Rax2p to the division site did not appear to depend on Bud9p, normal localization of Bud9p appeared largely or entirely dependent on Rax1p and Rax2p. Taken together, the results indicate that Rax1p and Rax2p interact closely with each other and with Bud8p and Bud9p in the establishment and/or maintenance of the cortical landmarks for bipolar budding.