title: High-throughput screening AlphaScreen assay for identification of small-molecule inhibitors of ubiquitin E3 ligase SCFSkp2-Cks1.
abstract: Decreased levels of cell cycle inhibitor p27(Kip1) due to excessive degradation occur in a variety of aggressive human tumors. Since reduced p27(Kip1) expression has been associated with a poor prognosis in many human cancers and resistance to certain antitumor therapies, elevation of p27(Kip1) expression could improve prognosis and prevent excessive cell proliferation. SCF(Skp2) is one of the major ubiquitin E3 ligases responsible for degradation of p27(Kip1). Ubiquitination of p27(Kip1) also requires a small adaptor protein, Cks1, which facilitates substrate recruitment by bridging the interaction between Skp2 and p27(Kip1). It has been shown previously that a direct interaction between Cks1 and Skp2 is required for p27(Kip1) degradation. Accordingly, perturbation of the Skp2-Cks1 interaction may represent an attractive target for pharmacological intervention. Here we describe a high-throughput AlphaScreen assay for discovering small-molecule inhibitors of the Skp2-Cks1 protein-protein interaction in vitro. Two compounds (NSC689857 and NSC681152) were identified and validated through a structure-activity relationship analysis. Both compounds were also shown to inhibit p27(Kip1) ubiquitination in vitro. These studies demonstrate that disruption of the Skp2-Cks1 interaction provides a viable strategy to prevent p27(Kip1) ubiquitination and may potentially be useful for the control of excessive degradation of this cell cycle inhibitor in tumor cells.
authors.affiliation: Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO, USA.
authors.forename: Dana
authors.initials: D
authors.lastname: Ungermannova
authors.forename: Junglim
authors.initials: J
authors.lastname: Lee
authors.forename: Gan
authors.initials: G
authors.lastname: Zhang
authors.forename: H Garry
authors.initials: HG
authors.lastname: Dallmann
authors.forename: Charles S
authors.initials: CS
authors.lastname: McHenry
authors.forename: Xuedong
authors.initials: X
authors.lastname: Liu
mesh_terms: D001565:Benzoates / Q000032:analysis / Q000378:metabolism; D042846:CDC2-CDC28 Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D004354:Drug Screening Assays, Antitumor / Q000379:methods*; D057166:High-Throughput Screening Assays / Q000379:methods*; D006801:Humans; D006873:Hydroquinones / Q000032:analysis / Q000378:metabolism; D009369:Neoplasms / Q000378:metabolism; D011485:Protein Binding; D044786:S-Phase Kinase-Associated Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D013329:Structure-Activity Relationship; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors*; D054875:Ubiquitination / Q000187:drug effects; D062366:para-Aminobenzoates / Q000032:analysis / Q000378:metabolism
chemical_list: D001565:Benzoates; C093090:CKS1B protein, human; D006873:Hydroquinones; C587492:NSC681152; C587491:NSC689857; D044786:S-Phase Kinase-Associated Proteins; D062366:para-Aminobenzoates; D050760:Cyclin-Dependent Kinase Inhibitor p27; D044767:Ubiquitin-Protein Ligases; D042846:CDC2-CDC28 Kinases
keywords: Cks1; E3 ligase; Skp2; inhibitor; p27kip1; proteolysis; ubiquitin