Ansari Khairul I, Mishra Bibhu P, Mandal Subhrangsu S
Department of Chemistry and Biochemistry, The University of Texas at Arlington, Arlington, Texas 76019, USA.
Biochim Biophys Acta. 2008 Jan;1779(1):66-73. doi: 10.1016/j.bbagrm.2007.11.006. Epub 2007 Dec 3.
Human encodes several histone H3-Lysine 4 (H3K4) specific methyl-transferases (HMTs) such as MLL1 (mixed lineage leukemia 1), MLL2, MLL3, hSet1 etc, that play critical roles in gene expression. These HMTs are present as distinct multi-protein complexes with several proteins in common. Herein, we have affinity purified and characterized human CpG binding protein (CGBP) and its interacting proteins from human cells. We demonstrated that CGBP is co-purified with three H3K4 specific HMTs MLL1, MLL2, and hSet1. We also performed independent immuno-precipitation of MLL1, MLL2 and hSet1 complexes from human cell and demonstrated that each of these complexes contains CGBP. In addition, CGBP is co-localized with MLL1, MLL2 and hSet1 in vivo and binds to the promoter of MLL target gene HoxA7. Antisense mediated knock down of CGBP diminished the recruitment of MLL1 and down regulated levels of H3K4 trimethylation in HoxA7 promoter affecting its expression. These results demonstrated that CGBP interacts with MLL1, MLL2 as well as hSet1 HMTs and plays critical roles in regulations of MLL target genes.
人类编码多种组蛋白H3赖氨酸4（H3K4）特异性甲基转移酶（HMT），如MLL1（混合谱系白血病1）、MLL2、MLL3、hSet1等，它们在基因表达中起关键作用。这些HMT以不同的多蛋白复合物形式存在，有几种蛋白质是共同的。在此，我们从人类细胞中亲和纯化并鉴定了人类CpG结合蛋白（CGBP）及其相互作用蛋白。我们证明CGBP与三种H3K4特异性HMT即MLL1、MLL2和hSet1共纯化。我们还从人类细胞中对MLL1、MLL2和hSet1复合物进行了独立的免疫沉淀，并证明这些复合物中的每一个都含有CGBP。此外，CGBP在体内与MLL1、MLL2和hSet1共定位，并与MLL靶基因HoxA7的启动子结合。反义介导的CGBP敲低减少了MLL1的募集，并下调了HoxA7启动子中H3K4三甲基化水平，影响其表达。这些结果表明CGBP与MLL1、MLL2以及hSet1 HMT相互作用，并在MLL靶基因的调控中起关键作用。
