The winged helix/forkhead class of transcription factors is characterized by a 100-amino-acid, monomeric DNA-binding domain. The structure of the DNA-binding domain of one of the class members, hepatocyte nuclear factor 3 (HNF3), in a complex with a DNA target has been solved (Clark et al. 1993). The DNA-binding domain folds into a variant of the helix–turn–helix motif and is made up of three helices and two characteristic large loops, or “wings.” Therefore, the DNA-binding motif has been named the winged helix DNA-binding domain.

Over the past 9 years since the identification of the first member of this class, the Drosophila melanogaster gene Fork head,> 100 members of this gene family have been identified (for review, see Kaufmann and Knöchel 1996) in species ranging from yeast to human. The rapid accumulation of sequences by many different laboratories has led to the use of multiple names and classification systems, making it very difficult to follow the literature and to name newly characterized winged helix/forkhead transcription factors. This problem was recognized and discussed at the first International Meeting on Forkhead/Winged Helix Proteins, held in La Jolla, California, in November 1998. At that time a proposal was developed to standardize the nomenclature for these proteins. Fox (Forkhead box) was adopted as the unified symbol for all chordate winged helix/forkhead transcription factors. A winged helix/forkhead nomenclature committee was elected to implement this proposal, in consultation with the community at large. This final proposal has been endorsed by> 20 scientists1 as well as the Human and Mouse Gene Nomenclature Committees.