Sox-4, an Sry-like HMG box protein, is a transcriptional activator in lymphocytes.
Previous studies in lymphocytes have described two DNA-binding HMG box proteins, TCF-1 and LEF-1, with affinity for the A/TA/TCAAAG motif found in several T cell-specific enhancers. Evaluation of cotransfection experiments in non-T cells and the observed inactivity of an AACAAAG concatamer in the TCF-1/LEF-1-expressing T cell line BW5147, led us to conclude that these two proteins did not mediate the observed enhancer effect. We therefore searched for additional HMG box proteins. By a PCR-aided strategy, we cloned Sox-4, a gene with homology to the HMG box region of the sex determining gene SRY. Sox-4 was expressed in T and pre-B lymphocyte lines and in the murine thymus. Significantly, BW5147 T cells did not express Sox-4. Recombinant Sox-4 bound with high affinity (Kd 3 x 10(-11) M) to the minor groove of the AACAAAG motif, most likely contacting all seven base pairs. In contrast with observations on TCF-1 and LEF-1, cotransfection with Sox-4 unveiled a transactivating capacity, which mapped to its serine-rich C terminus. This region remained functional upon grafting onto a GAL4 DNA-binding domain. Sox-4 is thus the first 'classical' transcription factor in the Sox gene family with separable DNA-binding and transactivation domains. Our observations indicate that a detailed understanding of T cell-specific gene control must integrate the concerted activity of at least three tissue-specific HMG box genes.
van de Wetering
M
M
Department of Immunology, University Hospital Utrecht, The Netherlands.
Oosterwegel
M
M
van Norren
K
K
Clevers
H
H
D000595:Amino Acid Sequence; D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006609:High Mobility Group Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D009928:Organ Specificity / Q000235:genetics; D055751:SOXC Transcription Factors; D017385:Sequence Homology; D051876:Sex-Determining Region Y Protein; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; D009687:Nuclear Proteins; C083431:SOX4 protein, human; D055751:SOXC Transcription Factors; C497745:SRY protein, human; D051876:Sex-Determining Region Y Protein; C489990:Sox4 protein, mouse; C497746:Sry protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; D004247:DNA