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Pin1‐mediated Sp1 Phosphorylation by CDK1 Increases Sp1 Stability and Decreases its DNA Binding Activity during Mitosis
Author(s) -
Hung JanJong,
Yang HangChe
Publication year - 2015
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.29.1_supplement.724.17
Subject(s) - phosphorylation , pin1 , cyclin dependent kinase 1 , mitosis , cell cycle , microbiology and biotechnology , chemistry , isothermal titration calorimetry , biology , biochemistry , cell , isomerase , gene
We previously showed that Sp1 phosphorylation at Thr739 decreases its DNA binding activity. In this study, we found that phosphorylation of Sp1 at Thr739 alone is necessary, but not essential for the inhibition of its DNA binding activity during mitosis. Further study showed that Pin1 could be recruited to the Thr739(p)‐Pro motif of Sp1 to modulate the interaction between phospho‐Sp1 and CDK1, thereby CDK1‐mediated phosphorylation of Sp1 at Ser720, Thr723 and Thr737 during mitosis. Loss of the C‐terminal end of Sp1 (741‐785 aa) significantly increased Sp1 phosphorylation, implying that the C‐terminus inhibits CDK1‐mediated Sp1 phosphorylation. Binding analysis of Sp1 peptides to Pin1 by isothermal titration calorimetry indicated that Pin1 interacted with Thr739(p)‐Sp1 peptide but not with Thr739‐Sp1 peptide. X‐ray crystallography data showed that the Thr739(p)‐Sp1 peptide occupies the active site of Pin1. Increased Sp1 phosphorylation by CDK1 during mitosis not only stabilized the Sp1 levels via decreasing interaction with RNF4 but also caused Sp1 to move out of the chromosomes completely via decreasing its DNA binding activity, facilitating cell cycle progression. Thus, Pin1‐mediated conformational changes in the C‐terminal region of Sp1 are critical for increased CDK1‐mediated Sp1 phosphorylation to facilitate cell cycle progression during mitosis.