Figure 5.

Mechanism of nucleotide excision repair and its control by the circadian clock.A, molecular mechanism of mammalian Global and Transcription-Coupled Repair. Transcribed strand (TS) repair is predominantly determined by the phase of transcription of a given gene. The nontranscribed strand (NTS) repair is controlled by the repair enzyme complex oscillation, which is dictated by XPA damage recognition protein with a maximum at ZT10 for all genes regardless of the phase of transcription. B, schematic of the core clock that controls XPA expression. C, repair patterns of various gene's TS and NTS repair depending on whether they are constitutively expressed or controlled by the circadian clock, their phase of expression, and level of expression.