... significantly reduced the E-box bindingactivity of DEC1, although it did not affect the inter-action with BMAL1 or suppression of CLOCK/BM AL1-induced transcription. On the other hand, the basic region-deleted ... transcription. Fromthese findings, we conclude that the basic region, p artic-ularly the conserved A rg65, but not His57, is essential for the suppressive activity of DEC1.Determination of the binding ... of the basic region or of the bHLH domain completely abrogated the DEC1–BMAL1interaction, and substitution of Arg65 for Ala(DEC1:4–232-R65A) also abolished the in teraction, indicating thatthe...