Zeleznik-Le N J, Itoh-Lindstrom Y, Clarke J B, Moore T L, Ting J P
Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill 27599-7295.
J Biol Chem. 1992 Apr 15;267(11):7677-82.
The promoter of the major histocompatibility class II gene DRA contains an octamer element (ATTTGCAT) that is required for efficient DRA expression in B cells. Several DNA-binding proteins are known to bind this sequence. The best characterized are the B cell-specific OTF-2 and the ubiquitous OTF-1. This report directly demonstrates that OTF-2 but not OTF-1 regulates the DRA gene. In vitro transcription analysis using protein fractions enriched for the octamer-binding protein OTF-2 demonstrate a positive functional role for OTF-2 in DRA gene transcription. In contrast, OTF-1-enriched protein fractions did not affect DRA gene transcription although it functionally enhanced the transcription of another gene. Recombinant OTF-2 protein produced by in vitro transcription/translation could also enhance DRA gene transcription in vitro. In vivo transient transfection studies utilizing an OTF-2 expression vector resulted in similar findings: that OTF-2 protein enhanced DRA gene transcription, and that this effect requires an intact octamer element. Together these results constitute the first direct evidence of a positive role for the lymphoid-specific octamer-binding factor in DRA gene transcription.
主要组织相容性复合体II类基因DRA的启动子含有一个八聚体元件（ATTTGCAT），这是B细胞中DRA高效表达所必需的。已知有几种DNA结合蛋白能结合该序列。其中特征最明确的是B细胞特异性的OTF-2和普遍存在的OTF-1。本报告直接证明是OTF-2而非OTF-1调节DRA基因。使用富含八聚体结合蛋白OTF-2的蛋白组分进行的体外转录分析表明，OTF-2在DRA基因转录中具有正向功能作用。相比之下，富含OTF-1的蛋白组分虽能在功能上增强另一个基因的转录，但对DRA基因转录没有影响。通过体外转录/翻译产生的重组OTF-2蛋白在体外也能增强DRA基因转录。利用OTF-2表达载体进行的体内瞬时转染研究也得到了类似结果：OTF-2蛋白增强了DRA基因转录，且这种效应需要完整的八聚体元件。这些结果共同构成了淋巴细胞特异性八聚体结合因子在DRA基因转录中起正向作用的首个直接证据。
