tailieunhanh - Báo cáo khoa học: Functional analysis of the basic helix-loop-helix transcription factor DEC1 in circadian regulation

The basic helix-loop-helix transcription factor DEC1 is expressed in a circadian manner in the suprachiasmatic nucleus where it seems to play a role in regulating the mammalian circadian rhythm by suppressing the CLOCK/BMAL1-activated promoter. The interaction of DEC1 with BMAL1 has been suggested as one of the molecular mechanisms of the suppression [Honma, S., Kawamoto, T., Takagi, Y., Fujimoto, K., Sato, F., Noshiro, M., Kato, Y. & Honma, K. (2002)Nature419, 841–844]. | Eur. J. Biochem. 271 4409-4419 2004 FEBS 2004 doi Functional analysis of the basic helix-loop-helix transcription factor DEC1 in circadian regulation Interaction with BMAL1 Fuyuki Sato1 Takeshi Kawamoto1 Katsumi Fujimoto1 Mitsuhide Noshiro1 Kiyomasa K. Honda1 Sato Honma2 Ken-ichi Honma2 and Yukio Kato1 1 Department of Dental and Medical Biochemistry Hiroshima University Graduate School of Biomedical Sciences Hiroshima Japan department of Physiology Hokkaido University Graduate School of Medicine Sapporo Japan The basic helix-loop-helix transcription factor DEC1 is expressed in a circadian manner in the suprachiasmatic nucleus where it seems to play a role in regulating the mammalian circadian rhythm by suppressing the CLOCK BMAL1-activated promoter. The interaction of DEC1 with BMAL1 has been suggested as one of the molecular mechanisms of the suppression Honma S. Kawamoto T. Takagi Y. Fujimoto K. Sato F. Noshiro M. Kato Y. Honma K. 2002 Nature 419 841-844 . Deletion analysis of DEC1 demonstrated that its N-terminal region which includes the basic helix-loop-helix domain was essential for both the suppressive activity and the interaction with BMAL1 as DEC1 lacking the basic region did not show any suppression or interaction. Furthermore we found that Arg65 in the basic region which is conserved among group B basic helix-loop-helix proteins was responsible for the suppression for the interaction with BMAL1 and for its binding to CACGTG E-boxes. However substitution of His57 for Ala significantly reduced the E-box binding activity of DEC1 although it did not affect the interaction with BMAL1 or suppression of CLOCK BMAL1-induced transcription. On the other hand the basic region-deleted DEC1 acted in a dominant-negative manner for DEC1 activity indicating that the basic region was not required for homodimer formation of DEC1. Moreover mutant DEC1 also counteracted DEC2-mediated suppressive activity in a dominant-negative manner. The .