Renda Mario, Baglivo Ilaria, Burgess-Beusse Bonnie, Esposito Sabrina, Fattorusso Roberto, Felsenfeld Gary, Pedone Paolo V
Dipartimento di Scienze Ambientali, Seconda Università degli Studi di Napoli via Vivaldi 43, 81100 Caserta, Italy.
Laboratory of Molecular Biology, NIDDK, National Institutes of Health, Bethesda, Maryland 20892-0540.
J Biol Chem. 2007 Nov 16;282(46):33336-33345. doi: 10.1074/jbc.M706213200. Epub 2007 Sep 7.
The DNA-binding protein CTCF (CCCTC binding factor) mediates enhancer blocking insulation at sites throughout the genome and plays an important role in regulating allele-specific expression at the Igf2/H19 locus and at other imprinted loci. Evidence is also accumulating that CTCF is involved in large scale organization of genomic chromatin. Although CTCF has 11 zinc fingers, we show here that only 4 of these are essential to strong binding and that they recognize a core 12-bp DNA sequence common to most CTCF sites. By deleting individual fingers and mutating individual sites, we determined the orientation of binding. Furthermore, we were able to identify the specific finger and its point of DNA interaction that are responsible for the loss of CTCF binding when CpG residues are methylated in the imprinted Igf2/H19 locus. This single interaction appears to be critical for allele-specific binding and insulation by CTCF.
DNA结合蛋白CTCF（CCCTC结合因子）介导全基因组位点的增强子阻断绝缘作用，并在调控Igf2/H19基因座及其他印记基因座的等位基因特异性表达中发挥重要作用。越来越多的证据表明，CTCF参与基因组染色质的大规模组织。尽管CTCF有11个锌指结构，但我们在此表明，其中只有4个对强结合至关重要，且它们识别大多数CTCF位点共有的12碱基对核心DNA序列。通过删除单个锌指和突变单个位点，我们确定了结合方向。此外，我们能够确定在印记的Igf2/H19基因座中，当CpG残基甲基化时导致CTCF结合丧失的特定锌指及其与DNA的相互作用点。这种单一相互作用似乎对CTCF的等位基因特异性结合和绝缘至关重要。
