Manley N R, O'Connell M, Sun W, Speck N A, Hopkins N
Center for Cancer Research, Massachusetts Institute of Technology, Cambridge 02139.
J Virol. 1993 Apr;67(4):1967-75. doi: 10.1128/JVI.67.4.1967-1975.1993.
The transcriptional enhancers of the Moloney and Friend murine leukemia viruses (MLV) are important determinants of viral pathogenicity. We used electrophoretic mobility shift and methylation interference assays to study nuclear factors which bind to a region of these enhancers whose sequence is identical between Moloney and Friend viruses and particularly highly conserved among 35 mammalian type C retroviruses whose enhancer sequences have been aligned (E. Golemis, N. A. Speck, and N. Hopkins, J. Virol. 64:534-542, 1990). Previous studies identified sites for the leukemia virus factor b (LVb) and core proteins in this region (N. A. Speck and D. Baltimore, Mol. Cell. Biol. 7:1101-1110, 1987) as well as a site, overlapping those for LVb and core, for a third factor (N. R. Manley, M. A. O'Connell, P. A. Sharp, and N. Hopkins, J. Virol. 63:4210-4223, 1989). Surprisingly, the latter factor appeared to also bind two sites identified in the Friend MLV enhancer, Friend virus factor a and b1 (FVa and FVb1) sites, although the sequence basis for the ability of the protein to bind these diverse sites was not apparent. Here we describe the further characterization of this binding activity, termed MCREF-1 (for mammalian type C retrovirus enhancer factor 1), and the identification of a consensus sequence for its binding, GGN8GG. We also identify a factor, abundant in mouse T-cell lines and designated LVt, which binds to two sites in the Moloney MLV enhancer, overlapping the previously identified LVb and LVc binding sites. These sites contain the consensus binding site for the Ets family of proteins. We speculate on how distinct arrays of these factors may influence the disease-inducing phenotype.
莫洛尼氏和弗瑞德氏鼠白血病病毒（MLV）的转录增强子是病毒致病性的重要决定因素。我们利用电泳迁移率变动分析和甲基化干扰分析，研究了与这些增强子区域结合的核因子，该区域的序列在莫洛尼氏和弗瑞德氏病毒之间是相同的，并且在35种增强子序列已比对的哺乳动物C型逆转录病毒中尤其高度保守（E. 戈勒米斯、N. A. 斯佩克和N. 霍普金斯，《病毒学杂志》64:534 - 542, 1990）。先前的研究在该区域鉴定出了白血病病毒因子b（LVb）和核心蛋白结合位点（N. A. 斯佩克和D. 巴尔的摩，《分子与细胞生物学》7:1101 - 1110, 1987），以及与LVb和核心蛋白结合位点重叠的第三个因子结合位点（N. R. 曼利、M. A. 奥康奈尔、P. A. 夏普和N. 霍普金斯，《病毒学杂志》63:4210 - 4223, 1989）。令人惊讶的是，尽管该蛋白结合这些不同位点的序列基础并不明显，但后一个因子似乎也结合了在弗瑞德氏MLV增强子中鉴定出的两个位点，即弗瑞德病毒因子a和b1（FVa和FVb1）位点。在此，我们描述了这种结合活性（称为MCREF - 1，即哺乳动物C型逆转录病毒增强子因子1）的进一步特征，以及其结合的共有序列GGN8GG的鉴定。我们还鉴定出一种在小鼠T细胞系中丰富的因子，命名为LVt，它结合莫洛尼氏MLV增强子中的两个位点，与先前鉴定的LVb和LVc结合位点重叠。这些位点包含Ets家族蛋白的共有结合位点。我们推测这些因子的不同组合可能如何影响疾病诱导表型。
