Major histocompatibility complex class II transcriptional platform: Assembly of nuclear factor Y and regulatory factor X (RFX) on DNA requires RFX5 dimers
Major histocompatibility complex class II transcriptional platform: Assembly of nuclear factor Y and regulatory factor X (RFX) on DNA requires RFX5 dimers
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DOI：
10.1128/mcb.22.15.5616-5625.2002
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发表时间：
2002-08-01
影响因子：
5.3
通讯作者：
Peterlin, BM
中科院分区：
文献类型：
--
作者：
Jabrane-Ferrat, N;Nekrep, N;Peterlin, BM
主要组织相容性复合物 II 类 (MHC-II) 基因以 B 细胞特异性和 γ 干扰素诱导方式受到调节。其紧凑启动子中的保守上游序列 (CUS) 结合核因子 Y (NFY) 和调节因子 X (RFX) 复合物。这些 DNA 结合蛋白形成了一个吸引 II 类反式激活蛋白的平台，从而启动并延长 MHC-II 转录。在这份报告中，我们分析了这些 DNA 结合蛋白的复杂组装。首先，我们发现NFY可以与细胞中的RFX相互作用。特别地，NFYA和NFYC在体外结合RFXANK/B。接下来，RFX5在体内和体外形成二聚体。在 RFX5 DNA 结合结构域的富含亮氨酸的 N 端延伸段中，66 位的亮氨酸被发现对于这种自关联至关重要。不能形成二聚体的突变体RFX5蛋白也不支持体外CUS上或体内MHC-II转录上高阶DNA-蛋白复合物的形成。我们得出的结论是，MHC-II 转录平台开始在 CUS 上组装，然后通过多重、空间受限的相互作用结合 DNA。这些发现提供了一种解释，解释为什么在裸淋巴细胞综合征（一种先天性严重联合免疫缺陷）中，当 RFX 的任何亚基突变或缺失时，MHC-II 启动子是裸露的。
Major histocompatibility complex class II (MHC-II) genes are regulated in a B-cell-specific and gamma interferon-inducible manner. Conserved upstream sequences (CUS) in their compact promoters bind nuclear factor Y (NFY) and regulatory factor X (RFX) complexes. These DNA-bound proteins form a platform that attracts the class II transactivator, which initiates and elongates MHC-II transcription. In this report, we analyzed the complex assembly of these DNA-bound proteins. First, we found that NFY can interact with RFX in cells. In particular, NFYA and NFYC bound RFXANK/B in vitro. Next, RFX5 formed dimers in vivo and in vitro. Within a leucine-rich stretch N-terminal to the DNA-binding domain in RFX5, the leucine at position 66 was found to be critical for this self-association. Mutant RFX5 proteins that could not form dimers also did not support the formation of higher-order DNA-protein complexes on CUS in vitro or MHC-II transcription in vivo. We conclude that the MHC-II transcriptional platform begins to assemble off CUS and then binds DNA via multiple, spatially constrained interactions. These findings offer one explanation of why in the Bare Lymphocyte Syndrome, which is a congenital severe combined immunodeficiency, MHC-II promoters are bare when any subunit of RFX is mutated or missing.