TAILIEUCHUNG - Báo cáo khoa học: Protein kinase CK2 activates the atypical Rio1p kinase and promotes its cell-cycle phase-dependent degradation in yeast

Using co-immunoprecipitation combined with MS analysis, we identified the a¢ subunit of casein kinase 2 (CK2) as an interaction partner of the atypical Rio1 protein kinase in yeast. Co-purification of Rio1p with CK2 from Dcka1 or Dcka2 mutant extracts shows that Rio1p preferentially interacts with Cka2p in vitro. | ễFEBS Journal Protein kinase CK2 activates the atypical Riolp kinase and promotes its cell-cycle phase-dependent degradation in yeast Michaela Angermayr1 z Elisabeth Hochleitner2 t Friedrich Lottspeich2 and Wolfhard Bandlow1 1 Department Biologie I Bereich Genetik Ludwig-Maximilians-Universitat Munchen Germany 2 Max-Planck-Institut for Biochemie Martinsried Germany Keywords atypicalprotein kinase casein kinase 2 substrate cell-cycle phase-dependent degradation protein-protein interactions Riol protein kinase Correspondence M. Angermayr E-mail Present address ac-Pharma AG Oberhaching Germany tWacker Chemie AG Burghausen Germany Received 16 May 2007 revised 11 July 2007 accepted 16 July 2007 doi Using co-immunoprecipitation combined with MS analysis we identified the a subunit of casein kinase 2 CK2 as an interaction partner of the atypical Rio1 protein kinase in yeast. Co-purification of Rio1p with CK2 from Dckal or Dcka2 mutant extracts shows that Rio1p preferentially interacts with Cka2p in vitro. The C-terminal domain of Rio1p is essential and sufficient for this interaction. Six C-terminally located clustered serines were identified as the only CK2 sites present in Rio1p. Replacement of all six serine residues by aspartate mimicking constitutive phosphorylation stimulates Rio1p kinase activity about twofold in vitro compared with wild-type or the corresponding S A 6 mutant proteins. Both mutant alleles S A 6 or S D 6 complement in vivo however growth of the RIO1 S A 6 mutant is greatly retarded and shows a cell-cycle phenotype whereas the behaviour of the RIO1 S D 6 mutant is indistinguishable from wild-type. This suggests that phosphorylation by protein kinase CK2 leads to moderate activation of Rio1p in vivo and promotes cell proliferation. Physiological studies indicate that phosphorylation by CK2 renders the Rio1 protein kinase susceptible to proteolytic degradation at the G1 S transition in .

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