Chen F E, Huang D B, Chen Y Q, Ghosh G
Department of Biology, University of California, San Diego, La Jolla 92093-0359, USA.
Nature. 1998 Jan 22;391(6665):410-3. doi: 10.1038/34956.
The NF-kappaB p50/p65 heterodimer is the classical member of the Rel family of transcription factors which regulate diverse cellular functions such as immune response, cell growth, and development. Other mammalian Rel family members, including the proteins p52, proto-oncoprotein c-Rel, and RelB, all have amino-terminal Rel-homology regions (RHRs). The RHR is responsible for the dimerization, DNA binding and cytosolic localization of these proteins by virtue of complex formation with inhibitor kappaB proteins. Signal-induced removal of kappaB inhibitors allows translocation of dimers to the cell nucleus and transcriptional regulation of kappaB DNA-containing genes. NF-kappaB specifically recognizes kappaB DNA elements with a consensus sequence of 5'-GGGRNYYYCC-3' (R is an unspecified purine; Y is an unspecified pyrimidine; and N is any nucleotide). Here we report the crystal structure at 2.9 A resolution of the p50/p65 heterodimer bound to the kappaB DNA of the intronic enhancer of the immunoglobulin light-chain gene. Our structure reveals a 5-base-pair 5' subsite for p50, and a 4-base-pair 3' subsite for p65. This structure indicates why the p50/p65 heterodimer interface is stronger than that of either homodimer. A comparison of this structure with those of other Rel dimers reveals that both subunits adopt variable conformations in a DNA-sequence-dependent manner. Our results explain the different behaviour of the p50/p65 heterodimer with heterologous promoters.
核因子-κB p50/p65异二聚体是Rel转录因子家族的经典成员，该家族调控多种细胞功能，如免疫反应、细胞生长和发育。其他哺乳动物Rel家族成员，包括p52蛋白、原癌蛋白c-Rel和RelB，都有氨基末端Rel同源区域（RHR）。RHR通过与抑制蛋白κB形成复合物，负责这些蛋白的二聚化、DNA结合和胞质定位。信号诱导的κB抑制剂去除使二聚体转位至细胞核，并对含κB DNA的基因进行转录调控。核因子-κB特异性识别具有5'-GGGRNYYYCC-3'（R为任意嘌呤；Y为任意嘧啶；N为任意核苷酸）共有序列的κB DNA元件。在此，我们报道了与免疫球蛋白轻链基因内含子增强子的κB DNA结合的p50/p65异二聚体在2.9埃分辨率下的晶体结构。我们的结构揭示了p50的一个5碱基对的5'亚位点和p65的一个4碱基对的3'亚位点。该结构表明了p50/p65异二聚体界面为何比任何一种同二聚体的界面更强。将该结构与其他Rel二聚体的结构进行比较，发现两个亚基均以DNA序列依赖的方式采用可变构象。我们的结果解释了p50/p65异二聚体与异源启动子的不同行为。
