Hikima Jun-ichi, Lennard Mara L, Wilson Melanie R, Miller Norman W, Clem L William, Warr Gregory W
Marine Biomedicine and Environmental Sciences Center, Department of Biochemistry and Molecular Biology, Medical University of South Carolina, Charleston, South Carolina, USA.
Physiol Genomics. 2005 Apr 14;21(2):144-51. doi: 10.1152/physiolgenomics.00312.2004. Epub 2005 Feb 15.
E proteins are essential for B lymphocyte development and function, including immunoglobulin (Ig) gene rearrangement and expression. Previous studies of B cells in the channel catfish (Ictalurus punctatus) identified E protein homologs that are capable of binding the muE5 motif and driving a strong transcriptional response. There are three E protein genes in mammals, HEB (TCF12), E2A (TCF3), and E2-2 (TCF4). The major expressed E proteins found in catfish B cells are homologs of HEB and of E2A. Here we sought to define the complete family of E protein genes in a teleost fish, Takifugu rubripes, taking advantage of the completed genome sequence. The catfish CFEB (HEB homolog) sequence identified homologous E-protein-encoding sequences in five scaffolds in the Takifugu genome database. Detailed comparative analysis with the human genome revealed the presence of five E protein homologs in Takifugu. Single genes orthologous to HEB and to E2-2 were identified. In contrast, two members of the E2A gene family were identified in Takifugu; one of these shows the alternative processing of transcripts that identifies it as the ortholog of the E12/E47-encoding mammalian E2A gene, whereas the second Takifugu E2A gene has no predicted alternative splice products. A novel fifth E protein gene (EX) was identified in Takifugu. Phylogenetic analysis revealed four E protein branches among vertebrates: EX, E2A, HEB, and E2-2.
E蛋白对于B淋巴细胞的发育和功能至关重要，包括免疫球蛋白（Ig）基因重排和表达。先前对斑点叉尾鮰（Ictalurus punctatus）B细胞的研究鉴定出了能够结合muE5基序并驱动强烈转录反应的E蛋白同源物。哺乳动物中有三个E蛋白基因，即HEB（TCF12）、E2A（TCF3）和E2-2（TCF4）。在斑点叉尾鮰B细胞中发现的主要表达的E蛋白是HEB和E2A的同源物。在这里，我们利用已完成的基因组序列，试图确定硬骨鱼红鳍东方鲀（Takifugu rubripes）中E蛋白基因的完整家族。斑点叉尾鮰CFEB（HEB同源物）序列在红鳍东方鲀基因组数据库的五个支架中鉴定出了同源的E蛋白编码序列。与人类基因组的详细比较分析揭示了红鳍东方鲀中存在五个E蛋白同源物。鉴定出了与HEB和E2-2直系同源的单基因。相比之下，在红鳍东方鲀中鉴定出了E2A基因家族的两个成员；其中一个显示出转录本的可变加工，将其鉴定为编码哺乳动物E12/E47的E2A基因的直系同源物，而第二个红鳍东方鲀E2A基因没有预测的可变剪接产物。在红鳍东方鲀中鉴定出了一个新的第五个E蛋白基因（EX）。系统发育分析揭示了脊椎动物中的四个E蛋白分支：EX、E2A、HEB和E-2。
