sentences:  However, because PER protein cannot directly bind to DNA, it does not directly influence its own transcription; alternatively, it inhibits its own activators.After PER is produced from per mRNA, it dimerizes with Timeless (TIM) and the complex goes into the nucleus and inhibits the transcription factors of "per" and "tim", the CLOCK/CYCLE heterodimer.This CLOCK/CYCLE complex acts as a transcriptional activator for "per" and "tim" by binding to specific enhancers (called E-boxes) of their promoters.