DEFINITION OF THE DNA-BINDING SPECIFICITY OF TTF-1 HOMEODOMAIN BY CHROMATOGRAPHIC SELECTION OF BINDING SEQUENCES

The homeodomain of the thyroid transcription factor-1 (TTF-1HD) shows a peculiar DNA-binding specificity, preferentially recognizing sequenc es having the 5'-CAAG-3' core motif. In order to detail the DNA-bindin g specificity of this protein, a TTF-1HD-Sepharose column chromatograp hy was used. A sequential selection and amplification of sequences was performed. TTF-IHD binding activity for selected and unselected seque nces was measured. The presence of the 5'-CAAG-3' core motif was neces sary, but not sufficient, to obtain the maximal binding activity for T TF-1HD. However, several of the selected sequences do not contain the 5'-CAAG-3' core motif and are bound by TTF-1HD only 2-fold less with r espect to sequences bound with the highest affinity. Therefore, these data indicate that TTF-1HD specifically recognizes a spectrum of seque nces wider than previously determined. (C) 1995 Academic Press, Inc.