Protein kinase CK2 interacts with and phosphorylates the Arabidopsis circadian clock-associated 1 protein.

The circadian clock-associated 1 (CCA1) gene encodes a Myb-related transcription factor that has been shown to be involved in the phytochrome regulation of Lhcb1*3 gene expression and in the function of the circadian oscillator in Arabidopsis thaliana. By using a yeast interaction screen to identify proteins that interact with CCA1, ...
we have isolated a cDNA clone encoding a regulatory (beta) subunit of the protein kinase CK2 and have designated it as CKB3. CKB3 is the only reported example of a third beta-subunit of CK2 found in any organism. CKB3 interacts specifically with CCA1 both in a yeast two-hybrid system and in an in vitro interaction assay. Other subunits of CK2 also show an interaction with CCA1 in vitro. CK2 beta-subunits stimulate binding of CCA1 to the CCA1 binding site on the Lhcb1*3 gene promoter, and recombinant CK2 is able to phosphorylate CCA1 in vitro. Furthermore, Arabidopsis plant extracts contain a CK2-like activity that affects the formation of a DNA-protein complex containing CCA1. These results suggest that CK2 can modulate CCA1 activity both by direct interaction and by phosphorylation of the CCA1 protein and that CK2 may play a role in the function of CCA1 in vivo.
Mesh Terms:
Amino Acid Sequence, Arabidopsis, Arabidopsis Proteins, Base Sequence, Casein Kinase II, Circadian Rhythm, DNA, Complementary, DNA, Recombinant, DNA-Binding Proteins, Molecular Sequence Data, Phosphorylation, Promoter Regions, Genetic, Protein Binding, Protein-Serine-Threonine Kinases, Recombinant Proteins, Sequence Homology, Amino Acid, Transcription Factors
Proc. Natl. Acad. Sci. U.S.A.
Date: Sep. 01, 1998
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