In vitro phosphorylation studies of a conserved region of the transcription factor ATF1.

A large family of mammalian transcription factors including multiple variants of CREB, CREM and ATF1 have been implicated in signal transduction by cAMP and other cellular pathways. Although the roles of some members of the family have been characterised the function of ATF1 is poorly understood. We have identified one or more key serine residues that are required for a phosphorylation-induced conformational change in ATF1. The critical serines map to a putative transcriptional activation domain of ATF1 and affect the stability of ATF1 DNA-binding. Intriguingly phosphorylation is modulated by ATF1 homodimerization and by ATF1 binding to DNA. One of the key serine residues required for ATF1 phosphorylation is not conserved in CREB and CREM suggesting that it is likely to determine some specialised function of ATF1.