Isolation and characterization of a novel zinc finger protein MIZF in DNA methylation and transcriptional regulation

MBD2是甲基- cpg结合蛋白家族的成员，在甲基化DNA沉默中起重要作用。我们最近发现了一种新的锌指蛋白MIZF，作为mbd2的结合伙伴。为了了解MIZF在mbd2介导的基因沉默中的生理功能，我们研究了MIZF及其潜在靶基因的dna结合特性。使用循环扩增和选择靶标技术，确定DNA序列CGGACGTT足以与MIZF结合。单个锌指的缺失表明，七个锌指中有五个是DNA结合所必需的。报告基因分析表明，MIZF抑制包含该DNA序列的启动子的转录。数据库检索表明，包括Rb在内的多种人类基因的启动子区域均含有该序列。MIZE实际上与Rb启动子内的识别序列结合并抑制Rb转录。这些结果表明，MIZF通过其dna结合活性，作为序列特异性转录抑制因子可能参与mbd2介导的表观遗传基因沉默。

MBD2 is a member of the methyl-CpG binding protein family that plays an important role in methylated DNA silencing. We have recently identified a novel zinc finger protein, MIZF, as an MBD2-binding partner. To understand the physiological function of MIZF in MBD2-mediated gene silencing, we investigated the DNA-binding properties of MIZF and its potential target genes. Using a cyclic amplification and selection of targets technique, the DNA sequence CGGACGTT was determined as sufficient for MIZF binding. Deletion of individual zinc fingers revealed that five of the seven zinc fingers are required for DNA binding. Reporter assays demonstrated that MIZF represses transcription from the promoter including this DNA sequence. Database search indicated that a variety of human genes including Rb contain this sequence in their promoter region. MIZE actually bound to its recognition sequence within the Rb promoter and repressed the Rb transcription. These results suggest that MIZF, through its DNA-binding activity, acts as a sequence-specific transcriptional repressor likely involved in MBD2-mediated epigenetic genesilencing.