The BMAL1 C terminus regulates the circadian transcription feedback loop.
The circadian clock is driven by cell-autonomous transcription/translation feedback loops. The BMAL1 transcription factor is an indispensable component of the positive arm of this molecular oscillator in mammals. Here, we present a molecular genetic screening assay for mutant circadian clock proteins that is based on real-time circadian rhythm monitoring in cultured fibroblasts. By using this assay, we identified a domain in the extreme C terminus of BMAL1 that plays an essential role in the rhythmic control of E-box-mediated circadian transcription. Remarkably, the last 43 aa of BMAL1 are required for transcriptional activation, as well as for association with the circadian transcriptional repressor CRYPTOCHROME 1 (CRY1), depending on the coexistence of CLOCK protein. C-terminally truncated BMAL1 mutant proteins still associate with mPER2 (another protein of the negative feedback loop), suggesting that an additional repression mechanism may converge on the N terminus. Taken together, these results suggest that the C-terminal region of BMAL1 is involved in determining the balance between circadian transcriptional activation and suppression.
Kiyohara
Yota B
YB
Center of Excellence, Unit of Circadian Systems, Department of Biological Sciences, Nagoya University Graduate School of Science, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
Tagao
Sayaka
S
Tamanini
Filippo
F
Morita
Akira
A
Sugisawa
Yukiko
Y
Yasuda
Maya
M
Yamanaka
Iori
I
Ueda
Hiroki R
HR
van der Horst
Gijsbertus T J
GT
Kondo
Takao
T
Yagita
Kazuhiro
K
D056930:ARNTL Transcription Factors; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D001681:Biological Assay; D056926:CLOCK Proteins; D002478:Cells, Cultured; D002940:Circadian Rhythm / Q000235:genetics*; D056931:Cryptochromes; D025461:Feedback, Physiological / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D005420:Flavoproteins / Q000378:metabolism; D005786:Gene Expression Regulation; D051379:Mice; D051381:Rats; D012097:Repressor Proteins / Q000378:metabolism; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation
D056930:ARNTL Transcription Factors; D051792:Basic Helix-Loop-Helix Proteins; D056926:CLOCK Proteins; D056931:Cryptochromes; D005420:Flavoproteins; D012097:Repressor Proteins; D015534:Trans-Activators; C538961:Bmal1 protein, mouse; C538964:Cry1 protein, mouse; C538965:Cry1 protein, rat; C538944:Clock protein, mouse; C538945:Clock protein, rat