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

S. Sugano, C. Andronis, R. M. Green, Z. Y. Wang, E. M. Tobin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

198 Scopus citations


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 (β) subunit of the protein kinase CK2 and have designated it as CKB3. CKB3 is the only reported example of a third β- 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 β-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.

Original languageAmerican English
Pages (from-to)11020-11025
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number18
StatePublished - 1 Sep 1998
Externally publishedYes


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