A comparison of the properties of So Sox - 1 and Sox - 2

in of e n factor containing a 79-amino-acid DNA-binding domain known as the HMG box (Capel and Lovell-Badge, 1993). Many genes have now been cloned on the basis of their homology to the HMG box of Sry and comprise the Sox gene family, for Sry-related HMG box-containing genes. Approximately 20 Sox genes have been found in mammals, with more being identified in other vertebrates and invertebrates such as Drosophila and C. elegans (Denny et al., 1992a; Wright et al., 1993; Laudet et al., 1993, Coriat et al., 1993; our unpublished results). The homology exhibited within the HMG box varies between members of the family but allows them to be grouped into different subfamilies. For example, the first Sox genes to be cloned, a1-a3 (now termed Sox1-3), are in the subfamily app ). ate orm it t Sox ce ( et al., 1993; Foster and Graves, 1994). In addition been mapped to the X chromosome in both these mam is relevant because the X and the Y chromosomes to have arisen from a common ancestor ‘autosome’ in that gave rise to mammals. However, given that there 20 mammalian Sox genes (e.g. Wright et al., 1993) an many more that have not yet been identified, the loca 3 on the X chromosome may be fortuitous. Sry could inated from any other Sox gene by gene duplication a cation or by retroposition. It would therefore informative to compare the properties exhibited by Sr 3 and other closely related members of the Sox gen order to determine how similar they are. y9x. e rxes e e e y. ois ges , w are pr s Sr tion he fro , th lo ies.