TY - JOUR
T1 - Essential roles of CKIδ and CKIε in the mammalian circadian clock
AU - Lee, Hyeongmin
AU - Chen, Rongmin
AU - Lee, Yongjin
AU - Yoo, Seunghee
AU - Lee, Choogon
PY - 2009/12/15
Y1 - 2009/12/15
N2 - Circadian rhythms in mammals are generated by a negative transcriptional feedback loop in which PERIOD (PER) is rate-limiting for feedback inhibition. Casein kinases Iδ and Iε (CKIδ/ε) can regulate temporal abundance/activity of PER by phosphorylation-mediated degradation and cellular localization. Despite their potentially crucial effects on PER, it has not been demonstrated in a mammalian system that these kinases play essential roles in circadian rhythm generation as does their homolog in Drosophila. To disrupt both CKIδ/ε while avoiding the embryonic lethality of CKIδ disruption in mice, we used CKIδ-deficient Per2Luc mouse embryonic fibroblasts (MEFs) and overexpressed a dominant-negative mutant CKIε (DN-CKIε) in the mutant MEFs. CKIδ-deficient MEFs exhibited a robust circadian rhythm, albeit with a longer period, suggesting that the cells possess a way to compensate for CKIδ loss. When CKIε activity was disrupted by the DN-CKIε in the mutant MEFs, circadian bioluminescence rhythms were eliminated and rhythms in endogenous PER abundance and phosphorylation were severely compromised, demonstrating that CKIδ/ε are indeed essential kinases for the clockwork. This is further supported by abolition of circadian rhythms when physical interaction between PER and CKIδ/ε was disrupted by overexpressing the CKIδ/ε binding domain of PER2 (CKBD-P2). Interestingly, CKBD-P2 overexpression led to dramatically low levels of endogenous PER, while PER-binding, kinase-inactive DN-CKIε did not, suggesting that CKIδ/ε may have a non-catalytic role in stabilizing PER. Our results show that an essential role of CKIδ/ε is conserved between Drosophila and mammals, but CKIδ/ε and DBT may have divergent noncatalytic functions in the clockwork as well.
AB - Circadian rhythms in mammals are generated by a negative transcriptional feedback loop in which PERIOD (PER) is rate-limiting for feedback inhibition. Casein kinases Iδ and Iε (CKIδ/ε) can regulate temporal abundance/activity of PER by phosphorylation-mediated degradation and cellular localization. Despite their potentially crucial effects on PER, it has not been demonstrated in a mammalian system that these kinases play essential roles in circadian rhythm generation as does their homolog in Drosophila. To disrupt both CKIδ/ε while avoiding the embryonic lethality of CKIδ disruption in mice, we used CKIδ-deficient Per2Luc mouse embryonic fibroblasts (MEFs) and overexpressed a dominant-negative mutant CKIε (DN-CKIε) in the mutant MEFs. CKIδ-deficient MEFs exhibited a robust circadian rhythm, albeit with a longer period, suggesting that the cells possess a way to compensate for CKIδ loss. When CKIε activity was disrupted by the DN-CKIε in the mutant MEFs, circadian bioluminescence rhythms were eliminated and rhythms in endogenous PER abundance and phosphorylation were severely compromised, demonstrating that CKIδ/ε are indeed essential kinases for the clockwork. This is further supported by abolition of circadian rhythms when physical interaction between PER and CKIδ/ε was disrupted by overexpressing the CKIδ/ε binding domain of PER2 (CKBD-P2). Interestingly, CKBD-P2 overexpression led to dramatically low levels of endogenous PER, while PER-binding, kinase-inactive DN-CKIε did not, suggesting that CKIδ/ε may have a non-catalytic role in stabilizing PER. Our results show that an essential role of CKIδ/ε is conserved between Drosophila and mammals, but CKIδ/ε and DBT may have divergent noncatalytic functions in the clockwork as well.
KW - Casein kinase
KW - Delta
KW - Dominant-negative mutant
KW - Epsilon
KW - PERIOD
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UR - http://www.scopus.com/inward/citedby.url?scp=75849128796&partnerID=8YFLogxK
U2 - 10.1073/pnas.0906651106
DO - 10.1073/pnas.0906651106
M3 - Article
C2 - 19948962
AN - SCOPUS:75849128796
SN - 0027-8424
VL - 106
SP - 21359
EP - 21364
JO - Proceedings of the National Academy of Sciences of the United States of America
JF - Proceedings of the National Academy of Sciences of the United States of America
IS - 50
ER -