CAMP responsive element binding protein 1, also known as CREB-1, plays multiple functions as a transcription factor in gene regulation. This protein is a CREB transcription factor that is a member of the leucine zipper family of DNA-binding proteins. CREB1 proteins are also known to be expressed in several spliced isoforms that act as transcriptional activators or repressors. The activator isoforms, possessing the functional domains for kinase induction and for interaction with other transcriptional regulators, act as transcriptional activators.The protein is phosphorylated by several protein kinases, and induces transcription of genes in response to hormonal stimulation of the cAMP pathway. CREB-1 has a complex influence on behavioural responses to drugs of abuse which varies depending on the brain region in which it is expressed. CREB-1 is important for serotonin (5-HT)-induced long-term facilitation (LTF) of the sensorimotor synapse in Aplysia.