Specific interaction between casein kinase 2 and the nucleolar protein Nopp140.
Casein kinase 2 (CK2) is a multifunctional second messenger-independent protein serine/threonine kinase that phosphorylates many different proteins. To understand the function and regulation of this enzyme, biochemical methods were used to search for CK2-interacting proteins. Using immobilized glutathione S-transferase fusion proteins of CK2, the nucleolar protein Nopp140 was identified as a CK2-associated protein. It was found that Nopp140 binds primarily to the CK2 regulatory subunit, beta. The possible in vivo association of Nopp140 with CK2 was also suggested from a coimmunoprecipitation experiment in which Nopp140 was detected in immunoprecipitates of CK2 prepared from cell extracts. Further studies using an overlay technique with radiolabeled CK2 as a probe revealed a direct CK2-Nopp140 interaction. Using deletion mutants of CK2beta subunits, the binding region of the CK2beta subunit to Nopp140 has been mapped. It was found that the NH2-terminal 20 amino acids of CK2beta are involved. Since Nopp140 has been identified as a nuclear localization sequence-binding protein and has been shown to shuttle between the cytoplasm and the nucleus, the finding of a CK2-Nopp140 interaction could shed light on our understanding of the function and regulation of CK2 and Nopp140.
Li
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D
Department of Pharmacology, University of Washington, Seattle, Washington 98195, USA.
Meier
U T
UT
Dobrowolska
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G
Krebs
E G
EG
D016475:3T3 Cells; D000818:Animals; D047390:Casein Kinase II; D002466:Cell Nucleolus / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D051379:Mice; D009687:Nuclear Proteins / Q000378:metabolism*; D010449:Peptide Mapping; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D017384:Sequence Deletion
D004268:DNA-Binding Proteins; C075564:NOLC1 protein, human; C513068:Nolc1 protein, mouse; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases