CBP/p300 is a cell type-specific modulator of CLOCK/BMAL1-mediated transcription.
BACKGROUND
Previous studies have demonstrated tissue-specific regulation of the rhythm of circadian transcription, suggesting that transcription factor complex CLOCK/BMAL1, essential for maintaining circadian rhythm, regulates transcription in a tissue-specific manner. To further elucidate the mechanism of the cell type-specific regulation of transcription by CLOCK/BMAL1 at the molecular level, we investigated roles of CBP/p300 and tissue-specific cofactors in CLOCK/BMAL1-mediated transcription.


RESULTS
As shown previously, CBP/p300 stimulates CLOCK/BMAL1-mediated transcription in COS-1 cells. However, CBP/p300 repressed CLOCK/BMAL1-mediated transcription in NIH3T3 cells and knockdown of CBP or p300 expression by siRNA enhanced this transcription. Studies using GAL4-fusion proteins suggested that CBP represses CLOCK/BMAL1-mediated transcription by targeting CLOCK. We further investigated mechanisms of this cell type-specific modulation of CLOCK/BMAL1-mediated transcription by CBP by examining roles of co-repressor HDAC3 and co-activator pCAF, which are highly expressed in NIH3T3 and COS cells, respectively. CBP repressed CLOCK/BMAL1-mediated transcription in COS-1 cells when HDAC3 was overexpressed, but activated it in NIH3T3 cells when pCAF was overexpressed. CBP forms a complex with CLOCK by interacting with HDAC3 or pCAF; however, direct interaction of CBP with CLOCK was not observed.


CONCLUSIONS
Our findings indicate possible mechanisms by which CBP/p300 tissue-specifically acts cooperatively with pCAF and HDAC3 either as a co-activator or co-repressor, respectively, for CLOCK/BMAL1.
Hosoda
Hiroshi
H
Department of Bioscience, Faculty of Applied Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo 156-8502, Japan. hhosoda@juntendo.ac.jp
Kato
Kenichi
K
Asano
Hidenori
H
Ito
Motonori
M
Kato
Haruno
H
Iwamoto
Taku
T
Suzuki
Akinobu
A
Masushige
Shoichi
S
Kida
Satoshi
S
D056930:ARNTL Transcription Factors / Q000378:metabolism*; D000818:Animals; D056926:CLOCK Proteins / Q000378:metabolism*; D019556:COS Cells; D050882:CREB-Binding Protein / Q000378:metabolism*; D002522:Chlorocebus aethiops; D050881:E1A-Associated p300 Protein / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D006655:Histone Deacetylases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D051379:Mice; D008957:Models, Genetic; D041681:NIH 3T3 Cells; D009928:Organ Specificity; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013329:Structure-Activity Relationship; D014158:Transcription, Genetic; D050880:p300-CBP Transcription Factors / Q000378:metabolism; D000099224:p300-CBP-Associated Factor; D000099186:Histone Deacetylase 3
D056930:ARNTL Transcription Factors; D056926:CLOCK Proteins; D050882:CREB-Binding Protein; D050881:E1A-Associated p300 Protein; D006655:Histone Deacetylases; D050880:p300-CBP Transcription Factors; D000099224:p300-CBP-Associated Factor; D000099186:Histone Deacetylase 3; C538961:Bmal1 protein, mouse; C538944:Clock protein, mouse; C494361:Ep300 protein, mouse