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Proc Natl Acad Sci U S A. 1995 May 23;92(11):5022-6.

Molecular cloning and characterization of a conserved nuclear serine(threonine) protein kinase.

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Friedrich Miescher-Institut, Basel, Switzerland.


Human, Drosophila melanogaster, and Caenorhabditis elegans cDNA clones encoding homologues of a serine(threonine) protein kinase (EC (designated Ndr protein kinase) have been isolated and sequenced. The human and Drosophila cDNAs predict polypeptides of 54 kDa and 52 kDa, respectively, which share approximately 80% amino acid similarity. Northern analysis of human tissues revealed a ubiquitously expressed 3.9-kb transcript. Recombinant GST-Ndr underwent intramolecular autophosphorylation on serine and threonine residues in vitro but failed to transphosphorylate several standard protein kinase substrates. Transfection of the human cDNA into COS-1 cells resulted in the appearance of an intense nuclear staining in cells analyzed by indirect immunofluorescence; deletion mutagenesis identified a short basic peptide, KRKAETWKRNRR, responsible for the nuclear accumulation of Ndr. Thus, Ndr is a conserved and widely expressed nuclear protein kinase. The closest known relative of this previously uncharacterized kinase is Dbf2, a budding yeast protein kinase required for the completion of nuclear division.

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