Hikima Jun-ichi, Lennard Richard Mara L, Wilson Melanie R, Miller Norman W, Warr Gregory W
Medical University of South Carolina, Marine Biomedicine and Environmental Sciences Center, Charleston, SC 29425, USA.
Mol Immunol. 2008 Feb;45(4):1165-70. doi: 10.1016/j.molimm.2007.08.001. Epub 2007 Sep 17.
E-proteins are essential class I bHLH transcription factors that play a role in lymphocyte development. In catfish lymphocytes the predominant E-proteins expressed are CFEB (a homologue of HEB) and E2A1, which both strongly drive transcription. In this study the role of homodimerization versus heterodimerization in the function of these catfish E-proteins was addressed through the use of expression constructs encoding forced dimers. Constructs expressing homo- and heterodimers were transfected into catfish B cells and shown to drive transcription from the catfish IGH enhancer. Expression from an artificial promoter containing a trimer of muE5 motifs clearly demonstrated that the homodimer of E2A1 drove transcription more strongly (by a factor of 10-25) than the CFEB homodimer in catfish B and T cells, while the heterodimer showed intermediate levels of transcriptional activation. Both CFEB1 and E2A1 proteins dimerized in vitro, and the heterodimer CFEB1-E2A1 was shown to bind the canonical muE5 motif.
E蛋白是一类重要的I型碱性螺旋-环-螺旋转录因子，在淋巴细胞发育中发挥作用。在鲶鱼淋巴细胞中，主要表达的E蛋白是CFEB（HEB的同源物）和E2A1，它们都能强烈驱动转录。在本研究中，通过使用编码强制二聚体的表达构建体，探讨了同二聚化与异二聚化在这些鲶鱼E蛋白功能中的作用。将表达同二聚体和异二聚体的构建体转染到鲶鱼B细胞中，结果表明它们能驱动鲶鱼IGH增强子的转录。含有三个muE5基序三聚体的人工启动子的表达清楚地表明，在鲶鱼B细胞和T细胞中，E2A1同二聚体驱动转录的能力比CFEB同二聚体更强（高出10至25倍），而异二聚体的转录激活水平处于中间。CFEB1和E2A1蛋白在体外都能形成二聚体，并且异二聚体CFEB1-E2A1被证明能结合典型的muE5基序。
