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Myc oncoproteins are phosphorylated by casein kinase II.

Lüscher, B and Kuenzel, E A and Krebs, E G and Eisenman, R N (1989) Myc oncoproteins are phosphorylated by casein kinase II. The EMBO journal, 8 (4). pp. 1111-1119. ISSN 0261-4189

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Casein kinase II (CK-II) is a ubiquitous protein kinase, localized to both nucleus and cytoplasm, with strong specificity for serine residues positioned within clusters of acidic amino acids. We have found that a number of nuclear oncoproteins share a CK-II phosphorylation sequence motif, including Myc, Myb, Fos, E1a and SV40 T antigen. In this paper we show that cellular myc-encoded proteins, derived from avian and human cells, can serve as substrates for phosphorylation by purified CK-II in vitro and that this phosphorylation is reversible. One- and two-dimensional mapping experiments demonstrate that the major phosphopeptides from in vivo phosphorylated Myc correspond to the phosphopeptides produced from Myc phosphorylated in vitro by CK-II. In addition, synthetic peptides with sequences corresponding to putative CK-II phosphorylation sites in Myc are subject to multiple, highly efficient phosphorylations by CK-II, and can act as competitive inhibitors of CK-II phosphorylation of Myc in vitro. We have used such peptides to map the phosphorylated regions in Myc and have located major CK-II phosphorylations within the central highly acidic domain and within a region proximal to the C terminus. Our results, along with previous studies on myc deletion mutants, show that Myc is phosphorylated by CK-II, or a kinase with similar specificity, in regions of functional importance. Since CK-II can be rapidly activated after mitogen treatment we postulate that CK-II mediated phosphorylation of Myc plays a role in signal transduction to the nucleus.

Item Type: Article or Abstract
Additional Information: This article is freely available in PubMed Central. No URL exists at the journal website.
PubMed ID: 2663470
PMCID: PMC400922
Grant Numbers: 83.503.0.87
Keywords or MeSH Headings: Amino Acid Sequence; Animals; Binding Sites; Casein Kinases; Humans; Molecular Sequence Data; Peptides; Phosphorylation; Protein Kinases/metabolism; Proto-Oncogene Proteins/metabolism; Proto-Oncogene Proteins c-myc; Signal Transduction;
Subjects: Molecules > Proteins > Enzymes
Cellular and Organismal Processes > Cell Physiology > Cell communication
Molecules > Molecular structure
Molecules > Genes > Oncogenes
Depositing User: Library Staff
Date Deposited: 03 Dec 2008 23:07
Last Modified: 21 May 2010 22:41

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