Sic1 is phosphorylated by CK2 on Ser201 in budding yeast cells.
We have previously identified Ser201 of Sic1, a yeast cyclin-dependent kinase inhibitor, as an in vitro target of protein kinase CK2. Here we present new evidence, by using specific anti-P-Ser201 antibodies and 2-D gel electrophoresis coupled to MALDI mass spectrometry analysis, that Sic1 is phosphorylated in vivo on Ser201 shortly after its de novo synthesis, during late anaphase in glucose-grown cells. This phosphorylation is also detected in Sic1 immunopurified from G1 cells. In agreement with these data we also show that the catalytic alpha' subunit of CK2, whose function is required for cell cycle progression, is detected in Sic1 immunopurified complexes, and that phosphorylation on Ser201 is reduced after CK2 inactivation at the non-permissive temperature in a cka1delta cka2(ts) yeast strain. These data strongly support the notion that CK2 phosphorylates Sic1 in vivo.
Coccetti
Paola
P
Dipartimento di Biotecnologie e Bioscienze, Università degli Studi Milano-Bicocca, P.zza della Scienza 2, 20126 Milano, Italy. paola.coccetti@unimib.it
Zinzalla
Vittoria
V
Tedeschi
Gabriella
G
Russo
Gian Luigi
GL
Fantinato
Sonia
S
Marin
Oriano
O
Pinna
Lorenzo A
LA
Vanoni
Marco
M
Alberghina
Lilia
L
D000595:Amino Acid Sequence; D047390:Casein Kinase II / Q000378:metabolism*; D020134:Catalytic Domain; D002453:Cell Cycle; D050756:Cyclin-Dependent Kinase Inhibitor Proteins; D008969:Molecular Sequence Data; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism*; D011485:Protein Binding; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D050756:Cyclin-Dependent Kinase Inhibitor Proteins; C086926:SIC1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D010768:Phosphoserine; D047390:Casein Kinase II