title: CK2 regulates in vitro the activity of the yeast cyclin-dependent kinase inhibitor Sic1.
abstract: We have previously demonstrated that the cyclin-dependent kinase inhibitor (Cki) Sic1 of Saccharomyces cerevisiae is phosphorylated in vitro by the CK2 kinase on Ser(201) residue. Moreover, we have collected evidence showing that Sic1 is functionally and structurally related to mammalian Cki p27(Kip1) and binds to the mammalian Cdk2/cyclin A complex with a similar mode of inhibition. In this paper, we use SPR analysis to investigate the binding of Sic1 to the catatytic and regulatory subunits of CK2. Evidence is presented showing that phosphorylation of Sic1 at the CK2 consensus site QES(201)EDEED increases the binding of a Sic1-derived peptide to the Cdk2/cyclin A complex, a functional homologue of the yeast Cdk1/Clb5,6. Moreover, Sic1 fully phosphorylated in vitro on Ser(201) by CK2 is shown to be a stronger inhibitor of the Cdk/cyclin complexes than the unphosphorylated protein. Taken together, these data disclose the possibility that CK2 plays a role in the regulation of Sic1 activity.
authors.affiliation: Dipartimento di Biotecnologie e Bioscienze, Università degli Studi di Milano-Bicocca, Italy.
authors.forename: Matteo
authors.initials: M
authors.lastname: Barberis
authors.forename: Mario A
authors.initials: MA
authors.lastname: Pagano
authors.forename: Luca De
authors.initials: LD
authors.lastname: Gioia
authors.forename: Oriano
authors.initials: O
authors.lastname: Marin
authors.forename: Marco
authors.initials: M
authors.lastname: Vanoni
authors.forename: Lorenzo A
authors.initials: LA
authors.lastname: Pinna
authors.forename: Lilia
authors.initials: L
authors.lastname: Alberghina
mesh_terms: D000596:Amino Acids; D047390:Casein Kinase II / Q000737:chemistry*; D019925:Cyclin A / Q000737:chemistry; D051357:Cyclin-Dependent Kinase 2 / Q000737:chemistry*; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D004789:Enzyme Activation; D007700:Kinetics; D008958:Models, Molecular; D010766:Phosphorylation; D011485:Protein Binding; D021122:Protein Subunits / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry*; D020349:Surface Plasmon Resonance; D013816:Thermodynamics
chemical_list: D000596:Amino Acids; D019925:Cyclin A; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D021122:Protein Subunits; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D047390:Casein Kinase II; D051357:Cyclin-Dependent Kinase 2