As a dimer, CREB-1 (cAMP-responsive element-binding protein 1) binds the cAMP response element (CRE), a sequence present in many viral and cellular promoters, to stimulate transcription. CREB-1 is activated by phosphorylayion on Ser-133 and Ser-142. Transcriptional activation is enhanced by the TORC coactivators which act independently of Ser-133 phosphorylation. CREB-1 has been implicated in synchronization of circadian rhythmicity. It interacts with various proteins including TORC/CRTC, CREBBP, ARRB1.