Editing Circadian clock (section)

=== Insect clocks ===
In ''D. melanogaster'', the gene cycle (CYC) is the orthologue of BMAL1 in mammals. Thus, CLOCK–CYC dimers activate the transcription of circadian genes. The gene timeless (TIM) is the orthologue for mammalian CRYs as the inhibitor; ''D. melanogaster'' CRY functions as a photoreceptor instead. In flies, CLK–CYC binds to the promoters of circadian-regulated genes only at the time of transcription. A stabilizing loop also exists where the gene vrille (VRI) inhibits whereas PAR-domain protein-1 (PDP1) activates Clock transcription.<ref name="Gallego">{{cite journal | vauthors = Gallego M, Virshup DM | title = Post-translational modifications regulate the ticking of the circadian clock | journal = Nature Reviews. Molecular Cell Biology | volume = 8 | issue = 2 | pages = 139–148 | date = February 2007 | pmid = 17245414 | doi = 10.1038/nrm2106 | s2cid = 27163437 }}</ref>