Protein phosphatase 2A is targeted to cell division control protein 6 by a calcium-binding regulatory subunit
Protein phosphatase 2A is targeted to cell division control protein 6 by a calcium-binding regulatory subunit
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DOI：
10.1074/jbc.m710313200
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发表时间：
2008-06-06
影响因子：
4.8
通讯作者：
Mumby, Marc C.
中科院分区：
文献类型：
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作者：
Davis, Anthony J.;Yan, Zhen;Mumby, Marc C.
细胞分裂控制蛋白6（Cdc 6）是DNA复制起点处复制前复合物形成所必需的。细胞周期蛋白依赖性激酶对Cdc 6的磷酸化抑制APC/C-cdh 1对Cdc 6的泛素化和蛋白酶体的降解。本文描述的实验表明，PPP 2 R3家族的调节亚基的PR 70成员将蛋白磷酸酶2A（PP 2A）靶向Cdc 6。与Cdc 6的相互作用由PR 70的C末端内的残基介导，而与PP 2A的相互作用需要PPP 2 R3家族内保守的N末端序列。两个功能性EF-手型钙结合基序介导PR 70与PP 2A的钙增强相互作用。钙对PR 70与Cdc 6的相互作用没有影响，但通过其对PR 70的作用增强PP 2A与Cdc 6的缔合。通过RNA干扰敲低PR 70导致内源性和表达的Cdc 6蛋白的积累，所述Cdc 6蛋白依赖于Cdc 6上的细胞周期蛋白依赖性蛋白激酶磷酸化位点。PR 70的敲低也导致G（1）阻滞，表明PR 70功能对于进入S期至关重要。这些观察结果表明，PP 2A可以通过PR 70亚基以钙调节的方式靶向Cdc 6，在那里它在调节蛋白磷酸化和稳定性方面发挥作用。
The cell division control protein 6 (Cdc6) is essential for formation of pre-replication complexes at origins of DNA replication. Phosphorylation of Cdc6 by cyclin-dependent kinases inhibits ubiquitination of Cdc6 by APC/C-cdh1 and degradation by the proteasome. Experiments described here show that the PR70 member of the PPP2R3 family of regulatory subunits targets protein phosphatase 2A (PP2A) to Cdc6. Interaction with Cdc6 is mediated by residues within the C terminus of PR70, whereas interaction with PP2A requires N-terminal sequences conserved within the PPP2R3 family. Two functional EF-hand calcium-binding motifs mediate a calcium-enhanced interaction of PR70 with PP2A. Calcium has no effect on the interaction of PR70 with Cdc6 but enhances the association of PP2A with Cdc6 through its effects on PR70. Knockdown of PR70 by RNA interference results in an accumulation of endogenous and expressed Cdc6 protein that is dependent on the cyclin-dependent protein kinase phosphorylation sites on Cdc6. Knockdown of PR70 also causes G(1) arrest, suggesting that PR70 function is critical for progression into S phase. These observations indicate that PP2A can be targeted in a calcium-regulated manner to Cdc6 via the PR70 subunit, where it plays a role in regulating protein phosphorylation and stability.