This model consists of two feedback loops.
In the first loop, LHY transcription has a light-induced component, that is dependent on the concentration of the unknown protein P, and a light-independent component that is activated by the unknown protein X. Nuclear LHY protein acts as a repressor of TOC1 transcription. Nuclear TOC1 protein activates protein X transcription and so indirectly activates LHY transcription, completing the loop. Protein P production is switched on during darkness and off during the light period.
In the second loop, nuclear TOC1 protein represses transcription of the unknown protein Y, and nuclear protein Y activates TOC1 transcription. Protein Y transcription is also light-dependent, being greater in the day. This effect is partly mediated by nuclear protein P.
The two loops are interlocked as nuclear LHY protein acts as a repressor of protein Y transcription.
All RNAs and proteins are degraded enzymatically, according to Michaelis-Menten kinetics. TOC1 protein degradation is inhibited by light. Protein P degradation has two components, a light-dependent linear process, and a light independent Michaelis-Menten process.
All proteins are translated and move reversibly between the nucleus and cytoplasm by linear processes.
This model has been published as Molecular Systems Biology doi: 10.1038/msb4100018