57Arg in the bHLH transcription factor DEC2 is essential for the suppression of CLOCK/BMAL2-mediated transactivation.

Substituting arginine 57 in DEC2 diminishes its suppressive activity on CLOCK/BMAL2-mediated transactivation.

• The basic helix-loop-helix transcription factors DEC2 and DEC1 are crucial for regulating circadian rhythms in the suprachiasmatic nucleus.
• Mammalian circadian rhythms are governed by molecular systems that involve a negative-feedback loop.
• CLOCK/BMAL1 and CLOCK/BMAL2 enhance DEC2 transcription through specific DNA sequences known as CACGTG E-boxes.
• Substituting arginine 57 for alanine or lysine in DEC2 reduces its ability to suppress CLOCK/BMAL2-mediated transactivation.
• Substituting proline 48 for alanine in DEC2 does not affect its suppressive activity.
• DEC2 and its substitution mutants are expressed at nearly the same levels, indicating that changes in activity are not due to differences in protein expression.

AI simplified