YY1's longer DNA-binding motifs.

The DNA-binding sites of YY1 located within two newly identified downstream genes of YY1, Peg3 (GGCGCCATnTT) and Xist (CCGCCATnTT), are longer than the known motif of YY1 (CGCCATnTT). Gel shift assays indicated that these DNA-binding sites are previously unnoticed, longer motifs of YY1. Independent DNA-binding motif studies further confirmed that YY1 recognizes a longer sequence (GCCGCCATTTTG) as its consensus motif. This longer motif exhibited higher affinity to the YY1 protein than the known motif. Another DNA-binding motif study was also performed using a protein containing three amino acid substitutions in the first zinc finger unit of YY1, mimicking the zinc finger domain of pho (a drosophila homologue of YY1). The substitutions cause the weakening of DNA-binding specificity at both 5'- and 3'-sides of the longer motif, yielding a much shorter sequence (GCCAT) as a consensus motif. This indicates that the intact first finger unit is required for recognition of the longer motif of YY1. Also, this shortening suggests that the DNA recognition by YY1 is mediated through the concerted, but not modular, contribution by its four zinc finger units.