&w. 161 (1995) 223-X c 1995 Else& Science B.V. All rights reserved. 0378-I 119~95/$09.50 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHG GENE 08998 Sequence and expression of Sax-18 encoding a new HMG-box transcription factor (Mouse; cloning; sr!s-related; cDNA) Timothy L. Dunn, Lesley Mynett-Johnson, Edwina M. Wright, Brett M. Hosking, Peter A. Koopman and George E.O. Muscat Received hy P.A. Manning: 17 November 1994; Revised/Accepted: 10 March 1995; Received at publishers: 18 April 1995 223 SUMMARY The newly identified Sax gene family @y-like HMG-box gene) is characterized by a conserved DNA sequence encoding a domain of approx. 80 amino acids (aa) which is responsible for sequence-specific DNA binding. The first member isolated, the mammalian Y-linked testis-determining gene, Sry, is necessary and sufficient for male development. We report here the identification of two new members of this family, Sax-I 7 and 18. We have determined the full cDNA sequence of Sox-18 which encodes a protein of 378 aa. Sox-18 mRNA transcripts were restricted to heart, lung and skeletal muscle in the adult mouse. - INTRODIJCTION The number of known members of the SOX gene family is rapidly increasing. Sox genes are characterised by a conserved DNA sequence encoding an approx. 80-aa domain responsible for sequence-specific DNA binding. This domain has homology with the HMG (high mobility group) box DNA-binding domain, originally identified in the transcription factor UBF (Jantzen et al., 1992). More than 60 different HMG-box proteins have been reported and/or entered into sequence data bases to date (Laudet et al., 1993). These fall into two broad categories, those with sequence-specific DNA-binding Corre.sponden~~e to: Dr. G.E.O. Muscat, Centre for Molecular and Cellular Biology. University of Queensland, St. Lucia. Brisbane 4075. Australia. Tel. (61-7 J 365-4492; Fax (6 l-7) 365-4388: e-mail: g.muscat@mailbox.uq.oz.au Abbreviations: aa, amino acid(s); bp. base pairs; cDNA. DNA comple- mentary to RNA; HMG, high mobilty group; kb, kilobasc(s) or 1000 bp; nt, nucleotide(s); LEF-1. lymphocyte enhancer factor; PCR, polymerase chain reaction; Sou. Srr like HMG-box gene; Sry, sex-related Y-chromosome gene: TCF-I, T-cell factor; UBF. upstream binding factor. SSIII 037X-l 119(95)003x0-4 activity (Sry, TCF-1, LEF-1 and the Sox proteins), and those which bind DNA in a sequence-independent manner (HMG protein. UBF). All known members of the sequence-specific group bind to variations of the WWCAAWG motif (Giese et al., 1991; Ferrari et al., 1992; Van de Wetering and Clevers, 1992 ). where W = A or T. The Sax (Sry like HMG box gene) family takes its name from the first member isolated, the mammalian Y-linked testis-determining gene, Sry. whose expres- sion in early embryogenesis is sufficient to cause the male development of a chromosomally female mouse (Koopman et al., 1991). In the course of cloning murine Sly, four other HMG-box genes expressed during embry- ogenesis were identified (Sex-I-4; Gubbay et al., 1990). Subsequent PCR cloning has now led to the identification of 18 different Sax genes in the mouse. most of which are as yet uncharacterised, and many of which have orthologues across the animal kingdom (Laudet et al., 1993. and references therein). A full length cDNA sequence has been reported for human zyxwvutsrqponmlkjihgfedc SRY (Sinclair et al., 1990), mouse Sax-4 and 5 (Denny et al., 1992; Van de Wetering et al., 1993), human and marsupial Sax-3 (Foster and Graves, 19941, and human TCF-1