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Structural mechanism of trimeric PR70 PP2A holoenzyme: insights into Cdc6 dephosphorylation
Author(s) -
Wlodarchak Nathan Joseph,
Guo Feng,
Satyshur Kenneth A,
Jiang Li,
Jeffrey Philip D,
Sun Tingwan,
Stanevich Vitali,
Mumby Marc C,
Xing Younga
Publication year - 2013
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.27.1_supplement.1043.2
Subject(s) - protein subunit , dephosphorylation , protein phosphatase 2 , heterotrimeric g protein , microbiology and biotechnology , chemistry , phosphorylation , specificity factor , biology , biochemistry , phosphatase , dna , signal transduction , g protein , polymerase , gene , rna dependent rna polymerase
Protein phosphatase 2A (PP2A) regulates many essential aspects of cellular function via diverse families of heterotrimeric holoenzymes. A regulatory subunit from the B” family plays a role in regulating the cellular level of Cdc6, a cell cycle regulator crucial for precise control of DNA replication licensing. No previous structural information for the B” family has been reported, and elucidating the interactions necessary for holoenzyme formation is critical in understanding how PP2A interacts with specific substrates. Here we report the high‐resolution three‐dimensional structure of the PR70 holoenzyme, and we show the B” subunit is an elongated EF‐hand calcium‐binding protein that stabilizes a remarkably compact holoenzyme conformation. The second EF‐hand of PR70 directly contacts the PP2A scaffold subunit and is buttressed by a protruding hydrophobic motif. A PR70 helix near the Cdc6‐binding region directly contacts the catalytic subunit, and this contact is required for the full activity of PR70 holoenzyme in dephosphorylation of the N‐terminal destruction motif of Cdc6. In contrast to PR70 holoenzyme, the holoenzyme involving the B’/B56/PR61 subunit is nearly inactive toward Cdc6. Our studies revealed important structural bases for the B” family of PP2A holoenzymes and mechanisms for precise control of Cdc6 dephosphorylation. This work was supported by University of Wisconsin‐Madison (Y. Xing), R01 GM096060–01 (Y. Xing), and GM86560 (M.C. Mumby), and T32 CA009135 (N. Wlodarchak).