How Drosophila Reacts to circadian rhythm? Jusl like in per gene, transcription in tim (timeless) gene is controlled with the same promoters (green and blue proteins). As PER and TIM proteins are made they interact with each other connecting together forming TIM/PER complex. As more and more TIM/PER complexes has been made, they enter nucleus, and interact with promoters, stopping expression of per/tim. As sun rises TIM gets degraded and translation reappears.