Two Independent Nuclear Localization Signals Are Present in the DNA-binding High-mobility Group Domains of SRY and SOX9

• Published in: The Journal of biological chemistry Vol. 272; no. 44; pp. 27848 - 27852
• Main Authors: Südbeck, Peter, Scherer, Gerd
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 31-10-1997; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Animals; Base Sequence; COS Cells; DNA Primers; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; High Mobility Group Proteins - genetics; High Mobility Group Proteins - metabolism; Humans; Molecular Sequence Data; Nuclear Localization Signals; Nuclear Proteins; Sex-Determining Region Y Protein; SOX9 Transcription Factor; Transcription Factors - genetics; Transcription Factors - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.272.44.27848

SRY and SOX9, members of the family of high-mobility group (HMG) domain transcription factors, are both essential for testis formation during human embryonic development. The HMG domain is a DNA-binding and DNA-bending motif comprising about 80 amino acid residues. It has been shown that SRY and SOX9 are nuclear proteins. Using normal or mutant SRY-β-galactosidase and SOX9-β-galactosidase fusion proteins in transfection studies involving COS-7 cells, we have identified two nuclear localization signals (NLSs) within the HMG domains of both proteins that can independently direct the fusion proteins into the nucleus. Only mutational inactivation of both NLS motifs resulted in complete exclusion of the fusion proteins from the nucleus. The NLS sequences are located at the N and C termini of the HMG domain and are a bipartite NLS motif and a basic cluster NLS motif, respectively. Both NLS motifs are conserved in the HMG domains of other transcription factors. The implications of the present results are discussed regarding (a) the apparent dual function of certain basic amino acid residues in the HMG domain of SRY in both DNA binding and in nuclear localization and (b) the possible control of SOX9 in early gonadal differentiation at the level of nuclear translocation.