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Abstract for Casein Kinase II
Casein Kinase II (CKII) is a ubiquitous serine/threonine protein kinase found
in eukaryotic cells. CKII is highly conserved among eukaryotes, including yeast,
Dictyostelium discoideum, C. elegans, Drosophila,
plants, bovines and humans. CKII is known also as phosvitin kinase, glycogen
synthase 5 kinase, troponin T kinase and casein kinase G. The diversity in
nomenclature reflects this kinase's broad range of substrates and its unique
ability to utilize GTP as well as ATP as the phosphate donor. Additional names
include casein kinase TS and protein kinase NII, which respectively indicate the
phosphorylation targets (threonine and serine residues) and the presence of this
kinase in the nucleus as well as in the cytoplasm and mitochondria. As this
complicated nomenclature suggests, CKII is a multifunctional protein kinase that
has been implicated in a variety of cellular processes and functions, including
mitosis and cellular transformation.
Several nuclear proteins, enzymes and transcription factors serve as
substrates for CKII. Phosphorylation by CKII in vitro alters the DNA binding or
catalytic activity of some of these substrates, which include: c-Myc, c-Myb,
serum response factor, c-Fos, c-Jun, DNA ligase, topoisomerase II, tumor
supressor proteins p53 and Rb, adenovirus E1A protein, human papilloma virus E7
protein, SV40 large T antigen, RNA polymerases I and II, nucleolar proteins B23
and C23, and several steroid hormone receptors. In addition some mitogens,
including insulin, insulin-like growth factor I, epidermal growth factor, serum
and phorbol esters rapidly increase the activity of CKII.
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