DOUBLETIME helps control CLOCK protein activity and gene regulation in the fruit fly's daily rhythm without using its enzyme function

DBT catalytic activity is not required for CLK phosphorylation or transcriptional repression.

• DBT is involved in the phosphorylation of the transcription factor CLK and the repressor PER within the circadian clock of fruit flies.
• The phosphorylation of PER is not necessary for the repression of CLK-dependent transcription.
• DBT may recruit other kinases to phosphorylate CLK, leading to transcriptional repression.
• The mechanisms observed in Drosophila could be similar in mammals due to the conservation of PER, DBT, and CLK functions.

Simplified