THE ROLE OF TRANSCRIPTION FACTORS IN CIRCADIAN GENE-EXPRESSION

There are three basic components present in all species which are esse ntial for the circadian gene expression; an input pathway which connec ts the clock to the environment, the clock oscillator, and an output p athway which connects the pacemaker to the resulting biological phenom ena. In this review, an attempt to separate the three processes will b e made from the molecular biological stand point. In the pineal of bir ds; Drosophila, and algae, cAMP/PKA pathway is functional in the outpu t, but in mammalian suprachiasmatic nucleus (SCN), this pathway includ ing the CREB/c-fos pathway, is believed to function in the input pathw ay. We propose here a model that easily explains the controversial res ults of the CREB/c-fos story in the SCN by considering this signal tra nsduction pathway as an output. Finally, we propose the importance of E-box and bHLH-PAS type transcription factors, in the clock oscillator in the SCN. (C) 1998 Elsevier Science Ireland Ltd. All rights reserve d.