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Mutations of the CK2 phosphorylation site of Sic1 affect cell size and S‐Cdk kinase activity in Saccharomyces cerevisiae
Author(s) -
Coccetti Paola,
Rossi Riccardo L.,
Sternieri Flora,
Porro Danilo,
Russo Gian Luigi,
Di Fonzo Andrea,
Magni Fulvio,
Vai Marco,
Alberghina Lilia
Publication year - 2004
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03836.x
Subject(s) - biology , serine , cyclin dependent kinase , alanine , phosphorylation , cell cycle , mutation , mutant , saccharomyces cerevisiae , kinase , biochemistry , microbiology and biotechnology , cell , amino acid , gene
Summary By sequence analysis we found an amino acid stretch centred on Serine 201 matching a stringent CK2 consensus site within the C‐terminal, inhibitory domain of Sic1. Here we show by direct mass spectrometry analysis that Sic1, but not a mutant protein whose CK2 phospho‐acceptor site has been mutated to alanine, Sic1 S201A , is actually phosphorylated in vitro by CK2 on Serine 201. Mutation of Serine 201 alters the coordination between growth and cell cycle progression. A significant increase of average protein content and of the average protein content at the onset of DNA synthesis is observed for exponentially growing cells harbouring the Sic1 S201A protein. A strong reduction of the same parameters is observed in cells harbouring Sic1 S201E . The deregulated coordination between cell size and cell cycle is also apparent at the level of S‐Cdk activity.