Submitted on April 30, 2008
Revised on May 28, 2008
Accepted on May 30, 2008
SOX17 DIRECTLY ACTIVATES ZFP202 TRANSCRIPTION DURING IN VITRO ENDODERM DIFFERENTIATION
Ethan S Patterson1*, Russell C Addis2, Michael J Shamblott2, and John D Gearhart2
1 Washington University School of Medicine
2 Johns Hopkins University
* To whom correspondence should be addressed. E-mail: espatterson{at}wustl.edu.
SOX17 is a SRY-related HMG box transcription factor that is necessary for endoderm formation in multiple species. Despite its essential function during endoderm formation and differentiation, few direct targets of SOX17 are known. To identify targets of SOX17, we isolated SOX17 binding sites using a chromatin immunoprecipitation (ChIP)-cloning screen. SOX17-ChIP identified zinc finger protein 202 (Zfp202) as a direct target of SOX17 during endoderm differentiation of F9 embryonal carcinoma cells. A sequence in the first intron of Zfp202 activated transcription in differentiated F9 cells and overexpression of Sox17 increased the transcriptional activity of this sequence. SOX17 binds to a site within this sequence in electrophoretic mobility shift assays and mutation of this site decreases the transcriptional activation. Zfp202 is induced concomitantly with Sox17 during endoderm differentiation of F9 cells. We also show that ZFP202 represses Hnf4a, which has been reported for the human ortholog ZNF202. Identifying targets of SOX17 will help to elucidate the molecular basis of endoderm differentiation and may provide a better understanding of the role of endoderm in patterning the other germ layers.
