Structure of the Ca2＋-dependent PP2A heterotrimer and insights into Cdc6 dephosphorylation  

作　　者：Nathan Wlodarchak Feng Guo Kenneth A Satyshur Li Jiang Philip D Jeffrey Tingwan Sun Vitali Stanevich Marc C Mumby Yongna Xing 

机构地区：[1]McArdle Laboratory, Department of Oncology, University of Wisconsin-Madison, School of Medicine and Public Health, Madi- son, WI, USA [2]Department of Molecular Biology, Princeton University, Princeton, NJ, USA [3]Department of Pharmacology, Uni- versity of Texas Southwestern Medical Center, Dallas, TX, USA

出　　处：《Cell Research》2013年第7期931-946,共16页细胞研究（英文版）

摘　　要：The B＂/PR72 family of protein phosphatase 2A （PP2A） is an important PP2A family involved in diverse cellular processes, and uniquely regulated by calcium binding to the regulatory subunit. The PR70 subunit in this family in- teracts with cell division control 6 （Cdc6）, a cell cycle regulator important for control of DNA replication. Here, we report crystal structures of the isolated PR72 and the trimeric PR70 holoenzyme at a resolution of 2.1 and 2.4 A, re- spectively, and in vitro characterization of Cdc6 dephosphorylation. The holoenzyme structure reveals that one of the PR70 calcium-binding motifs directly contacts the scaffold subunit, resulting in the most compact scaffold subunit conformation among all PP2A holoenzymes. PR70 also binds distinctively to the catalytic subunit near the active site, which is required for PR70 to enhance phosphatase activity toward Cdc6. Our studies provide a structural basis for unique regulation of B＂/PR72 holoenzymes by calcium ions, and suggest the mechanisms for precise control of sub- strate specificity among PP2A holoenzymes.The B＂/PR72 family of protein phosphatase 2A （PP2A） is an important PP2A family involved in diverse cellular processes, and uniquely regulated by calcium binding to the regulatory subunit. The PR70 subunit in this family in- teracts with cell division control 6 （Cdc6）, a cell cycle regulator important for control of DNA replication. Here, we report crystal structures of the isolated PR72 and the trimeric PR70 holoenzyme at a resolution of 2.1 and 2.4 A, re- spectively, and in vitro characterization of Cdc6 dephosphorylation. The holoenzyme structure reveals that one of the PR70 calcium-binding motifs directly contacts the scaffold subunit, resulting in the most compact scaffold subunit conformation among all PP2A holoenzymes. PR70 also binds distinctively to the catalytic subunit near the active site, which is required for PR70 to enhance phosphatase activity toward Cdc6. Our studies provide a structural basis for unique regulation of B＂/PR72 holoenzymes by calcium ions, and suggest the mechanisms for precise control of sub- strate specificity among PP2A holoenzymes.

关 键 词：protein phosphatase 2A regulatory subunit calcium-binding motif CDC6 cell cycle 

分 类 号：Q257[生物学—细胞生物学] Q26