Fig. 24.

Cellular redox status and CO-mediated regulation of circadian gene transcription. (A) Reducing redox status favors the heterodimerization of NPAS2 and BMAL1, forming an activated transcriptional complex for various circadian clock genes. (B) HO-2–generated CO (represented by the black dots) diffuses through cell membrane into the nucleus to bind to the heme domain of NPAS2, thereby deactivating the transcriptional complex. Figure reprinted with permission from Boehning and Snyder (2002).