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.
Sugano
S
S
Department of Molecular, Cell and Developmental Biology, University of California, Los Angeles, CA 90095-1606, USA.
Andronis
C
C
Green
R M
RM
Wang
Z Y
ZY
Tobin
E M
EM
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins; D001483:Base Sequence; D047390:Casein Kinase II; D002940:Circadian Rhythm; D018076:DNA, Complementary; D004274:DNA, Recombinant; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; C114425:CCA1 protein, Arabidopsis; D018076:DNA, Complementary; D004274:DNA, Recombinant; D004268:DNA-Binding Proteins; D011994:Recombinant Proteins; D014157:Transcription Factors; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases