Westerheide S D, Louis-Plence P, Ping D, He X F, Boss J M
Department of Microbiology and Immunology, Emory University School of Medicine, Emory University, Atlanta, GA 30322, USA.
J Immunol. 1997 May 15;158(10):4812-21.
The MHC class II homologous proteins HLA-DMA and HLA-DMB function in the loading of peptides onto class II molecules. Like the class II genes, the HLA-DM genes contain upstream regulatory sequences similar to the S-X-Y regulatory region as well as additional putative regulatory sites. To determine whether the DM genes are regulated in a similar manner as class II genes, a series of in vivo and in vitro analyses was performed. Deletion analysis showed that expression from the DM promoters is dependent on the conserved S-X-Y region. The class II-specific transcription factors RFX and CIITA are also required for expression, as cell lines deficient in these factors failed to allow transcription from the DM promoters. In addition, in vivo footprint analysis showed the putative X and Y boxes to be occupied by transcription factors in wild-type B cells, but not in RFX-deficient B cells. In astrocytes, IFN-gamma treatment induced increased occupancy of these sites. None of the other putative regulatory sites was occupied in vivo, indicating that they may not be functional. Finally, gel shift analysis showed synergistic complex formation between proteins that bind to the putative X boxes of the DM genes, as is found for the DRA gene. Therefore, the DM genes share a common mechanism of regulation with the class II genes.
MHC II类同源蛋白HLA - DMA和HLA - DMB在将肽装载到II类分子上发挥作用。与II类基因一样，HLA - DM基因包含与S - X - Y调控区相似的上游调控序列以及其他假定的调控位点。为了确定DM基因是否与II类基因以相似的方式受到调控，进行了一系列体内和体外分析。缺失分析表明，DM启动子的表达依赖于保守的S - X - Y区域。II类特异性转录因子RFX和CIITA对于表达也是必需的，因为缺乏这些因子的细胞系无法实现DM启动子的转录。此外，体内足迹分析表明，假定的X盒和Y盒在野生型B细胞中被转录因子占据，但在RFX缺陷的B细胞中则未被占据。在星形胶质细胞中，IFN - γ处理导致这些位点的占据增加。其他假定的调控位点在体内均未被占据，这表明它们可能没有功能。最后，凝胶迁移分析表明，与DM基因假定的X盒结合的蛋白质之间形成了协同复合物，DRA基因也有类似情况。因此，DM基因与II类基因共享一种共同的调控机制。
