IN-VITRO PHOSPHORYLATION STUDIES OF A CONSERVED REGION OF THE TRANSCRIPTION FACTOR ATF1

A large family of mammalian transcription factors including multiple v ariants of CREB, CREM and ATF1 have been implicated in signal transduc tion by cAMP and other cellular pathways. Although the roles of some m embers of the family have been characterised the function of ATF1 is p oorly understood. We have identified one or more key serine residues t hat are required for a phosphorylation-induced conformational change i n ATF1. The critical serines map to a putative transcriptional activat ion domain of ATF1 and affect the stability of ATF1 DNA-binding. Intri guingly phosphorylation is modulated by ATF1 homodimerisation and by A TF1 binding to DNA. One of the key serine residues required for ATF1 p hosphorylation is not conserved in CREB and CREM suggesting that it is likely to determine some specialised function of ATF1.