The Ubp15 deubiquitinase promotes timely entry into S phase in Saccharomyces cerevisiae.
The Ubp15 deubiquitinase promotes timely entry into S phase in Saccharomyces cerevisiae.
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DOI：
10.1091/mbc.e14-09-1400
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发表时间：
2015-06-15
影响因子：
3.3
通讯作者：
Solomon MJ
中科院分区：
文献类型：
--
作者：
Ostapenko D;Burton JL;Solomon MJ
S期细胞周期蛋白的积累调节DNA合成。在芽殖酵母中，S期细胞周期蛋白Clb 5在被后期促进复合物（APC）泛素化后在M期降解。Clb 5在G1中的积累是通过Ubp 15-去泛素化酶的去泛素化来促进的，Ubp 15-去泛素化酶对抗APC的作用。后期促进复合物与其激活剂Cdh 1是一种E3泛素连接酶，负责在G1期靶向细胞周期蛋白。在芽殖酵母Saccharomyces cerevisiae中，Cdh 1与去泛素化酶Ubp 15相关联，但这种相互作用的意义尚不清楚。为了更好地理解Ubp 15的生理作用，我们检查了缺乏Ubp 15的细胞的细胞周期表型。我们发现，ubp 15 β细胞表现出延迟的进展，从G1期进入S期和增加的敏感性，DNA合成抑制剂羟基脲。两种表型的ubp 15 β细胞被拯救的S期细胞周期蛋白基因CLB 5的额外副本。Clb 5是一种不稳定的蛋白质，通过几种途径靶向蛋白酶体介导的降解。我们发现，在G1期，APCCdh 1介导的降解Clb 5在ubp 15 cells中加速。Ubp 15与Clb 5的相互作用独立于Cdh 1和去泛素化Clb 5在重建系统。因此，Ubp 15的去泛素化抵消了APC对细胞周期蛋白Clb 5的活性，使Clb 5积累并及时进入S期。
The accumulation of S-phase cyclins regulates DNA synthesis. In budding yeast, the S-phase cyclin Clb5 is degraded in M phase after ubiquitination by the anaphase-promoting complex (APC). Clb5 accumulation in G1 is promoted by its deubiquitination by the Ubp15-deubiquitinating enzyme, which opposes the action of the APC. The anaphase-promoting complex in partnership with its activator, Cdh1, is an E3 ubiquitin ligase responsible for targeting cell cycle proteins during G1 phase. In the budding yeast Saccharomyces cerevisiae, Cdh1 associates with the deubiquitinating enzyme Ubp15, but the significance of this interaction is unclear. To better understand the physiological role(s) of Ubp15, we examined cell cycle phenotypes of cells lacking Ubp15. We found that ubp15∆ cells exhibited delayed progression from G1 into S phase and increased sensitivity to the DNA synthesis inhibitor hydroxyurea. Both phenotypes of ubp15∆ cells were rescued by additional copies of the S-phase cyclin gene CLB5. Clb5 is an unstable protein targeted for proteasome-mediated degradation by several pathways. We found that during G1 phase, the APCCdh1-mediated degradation of Clb5 was accelerated in ubp15∆ cells. Ubp15 interacted with Clb5 independent of Cdh1 and deubiquitinated Clb5 in a reconstituted system. Thus deubiquitination by Ubp15 counteracts APC activity toward cyclin Clb5 to allow Clb5 accumulation and a timely entry into S phase.