Kim Jeong do, Kim Joomyeong
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Genomics. 2009 Feb;93(2):152-8. doi: 10.1016/j.ygeno.2008.09.013. Epub 2008 Nov 8.
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.
YY1的DNA结合位点位于YY1的两个新鉴定的下游基因Peg3（GGCGCCATnTT）和Xist（CCGCCATnTT）内，比已知的YY1基序（CGCCATnTT）更长。凝胶迁移实验表明，这些DNA结合位点是以前未被注意到的、更长的YY1基序。独立的DNA结合基序研究进一步证实，YY1识别更长的序列（GCCGCCATTTTG）作为其共有基序。这个更长的基序对YY1蛋白的亲和力高于已知基序。还使用了一个在YY1的第一个锌指单元中含有三个氨基酸替换的蛋白进行了另一项DNA结合基序研究，该蛋白模拟了pho（YY1的果蝇同源物）的锌指结构域。这些替换导致在更长基序的5'和3'两侧的DNA结合特异性减弱，产生了一个短得多的序列（GCCAT）作为共有基序。这表明完整的第一个指单元是识别YY1更长基序所必需的。此外，这种缩短表明YY1对DNA的识别是通过其四个锌指单元协同而非模块化的作用介导的。
