Casein Kinase II Is Required for Cell Cycle Progression during G1 and G2/M in Saccharomyces cerevisiae

Abstract

The catalytic subunit of Saccharomyces cerevisiae casein kinase II (Sc CKII) is encoded by the CKA1 and CKA2 genes, which together are essential for viability. Five independent temperature-sensitive alleles of the CKA2 gene were isolated and used to analyze the function of CKII during the cell cycle. Following a shift to the nonpermissive temperature, cka2 ts strains arrested within a single cell cycle and exhibited a dual arrest phenotype consisting of 50% unbudded and 50% largebudded cells. The unbudded half of the arrested population contained a single nucleus and a single focus of microtubule staining, consistent with arrest in G 1 . Most of the large-budded fraction contained segregated chromatin and an extended spindle, indicative of arrest in anaphase, though a fraction contained an undivided nucleus with a short thick intranuclear spindle, indicative of arrest in G 2 and/or metaphase. Flow cytometry of pheromone-synchronized cells confirmed that CKII is required in G 1 , at a point which must lie at or beyond Start but prior to DNA synthesis. Similar analysis of hydroxyurea-synchronized cells indicated that CKII is not required for completion of previously initiated DNA replication but confirmed that the enzyme is again required for cell cycle progression in G 2 and/or mitosis. These results establish a role for CKII in regulation and/or execution of the eukaryotic cell cycle.Casein kinase II (CKII) 1 is a serine/threonine protein kinase which is ubiquitous among eukaryotic organisms (for review, see Issinger, 1993;Pinna, 1990;Tuazon and Traugh, 1991). The enzyme is composed of a catalytic ␣ and regulatory ␤ subunit that combine to form a native ␣ 2 ␤ 2 holoenzyme which is constitutively active in vitro. How (and indeed whether) the enzyme is regulated in vivo is unknown, though regulation via allosteric effectors (e.g. polyamines), covalent modification, cellular redistribution, and substrate-directed effects have all been proposed. CKII recognizes a Ser of Thr residue followed by a series of acidic residues and phosphorylates a broad and intriguing spectrum of both nuclear and cytoplasmic substrates.Although the physiological role of CKII is not known, several lines of evidence suggest a role for the enzyme in cell prolifer-

Bromodomain Factor 1 (Bdf1) Is Phosphorylated by Protein Kinase CK2

“…DNA sequencing of the protein coding region showed that the mutant had a single substitution: glycine 57 to aspartate (GGT3GAT). We also used the cka2-8 temperature-sensitive strain (provided by Clairborne Glover III [9]). It should be noted that these extracts were prepared from cells grown at the permissive temperature and the CK2 enzymes in these mutants are already partially defective at this temperature.…”

Phosphorylation regulates the stability of the regulatory CK2β subunit

“…Genetic studies in yeasts, worms and slime mold have demonstrated that CK2 is essential for viability (Hanna et al, 1995;Rethinaswamy et al, 1998;Kikkawa et al, 1992;Fraser et al, 2000). More detailed investigations of CK2 in yeast and in mammalian cells have further demonstrated that CK2 is required for cell cycle progression with roles at di erent stages in the cell cycle including G1, G1/S and G2/M (Hanna et al, 1995;Pepperkok et al, 1991;Lorenz et al, 1993). A role for CK2 in cellular responses to various stresses including UV, anisomycin, arsenite, heat shock and TNFa has also recently emerged (Sayed et al, 2000;Ghavidel and Schultz, 2001;Keller et al, 2001;Gerber et al, 2000).…”

Human herpesvirus 6B induces phosphorylation of p53 in its regulatory domain by a CK2- and p38-independent pathway

“…composed of two regulatory b subunits and two catalytic a and/or a9 subunits. The a and a9 subunits have significant homology in the N-terminal region, and may have complementary functions (Hanna et al, 1995). Knockout of CK2b is lethal in mice, due to complete abrogation of CK2 functions (Buchou et al, 2003).…”