Isotype specific regulation of lg class switching

LG 类别转换的同种型特异性调节

• 批准号: 7140383
• 负责人: Janet M. Stavnezer
• 金额: $ 27.77万
• 依托单位: UNIV OF MASSACHUSETTS MED SCH WORCESTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-15 至 2008-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7140383
• 关键词: B lymphocyte; DNA binding protein; chromatin immunoprecipitation; flow cytometry; gene rearrangement; genetic transcription; immunoglobulin A; immunoglobulin genes; immunoglobulin isotypes; laboratory mouse; methyltransferase; protein binding; tissue /cell culture

DESCRIPTION (provided by applicant): Upon activation by antigen, B cells undergo antibody class (isotype) switching, changing from expression of IgM to expression of IgG, IgA or IgE, while maintaining specificity for the same antigen. Since the isotype determines the effector function of the antibody, class switching allows the humoral immune response to adaptively respond to different infectious organisms. Class switching occurs by a DNA recombination event between switch (S) region sequences located upstream of each heavy chain constant (Ch) region gene. Numerous studies (including many from this laboratory) have established that transcription of specific unrearranged Ch genes occurs prior to switching and that this transcription is required for switching. Recent data, however, indicate that isotype specificity of switch recombination is regulated at additional undefined levels. Regulation of IgA switching is especially mysterious because it can only be induced to low levels in culture and yet is the most abundant antibody class in the body, expressed specifically in mucosal tissues. IgA is an important first line of defense against pathogens entering through body orifices. Data from our lab indicate that LSF/CP2/LBP-1c binds the switch (S) region DNA sequences associated with the IgA Ch gene and regulates switching to IgA in the l.29u B cell line. We have also found that the histone methyltransferase Suv39h1 specifically increases IgA switching in a plasmid switch substrate. The goal of this proposal is to investigate the mechanism of this regulation and to provide evidence for the hypothesis that chromatin accessibility and histone modifications of specific S regions regulate class switch recombination. In Aim 1 we propose to investigate the role of Suv39h1 in endogenous switch recombination and the mechanism of its function. We will investigate the hypothesis that Suv39h1 inhibits the activity of a sequence-specific DNA binding protein to repress switch recombination to IgA. The most likely candidate for this inhibitory protein is LSF/CP-2/LBP-1c, which is known to bind histone deacetylases and polychrome group proteins. Aim 2 will be to determine whether LSF specifically inhibits IgA switch recombination in normal splenic B cells and to examine the mechanism of inhibition of IgA switching by LSF.

描述（由申请人提供）：抗原激活后，B细胞会经历抗体类（同种型）切换，从IgM的表达转换为IgG，IgA或IgE的表达，同时保持对同一抗原的特异性。由于同种型决定抗体的效应函数，因此类切换允许体液免疫反应适应对不同的感染生物的反应。类开关是通过位于每个重链常数（CH）区域基因上游的开关区域序列之间的DNA重组事件发生的。大量研究（包括来自该实验室的许多研究）已经确定，在切换之前发生了特定透明的Ch基因的转录，并且此转录是切换所需的。然而，最近的数据表明，开关重组的同种型特异性在其他未定级水平下受到调节。 IgA转换的调节特别神秘，因为它只能诱导培养水平较低，但体内最丰富的抗体类别是专门在粘膜组织中表达的。 IGA是针对通过身体孔口进入的病原体的重要第一道防线。来自我们实验室的数据表明，LSF/CP2/LBP-1C结合了与IgA CH基因相关的开关区域DNA序列，并调节在L.29U B细胞系中切换到IGA。我们还发现，组蛋白甲基转移酶SUV39H1特别增加了质粒开关底物中的IgA开关。该提案的目的是研究该调节的机制，并为特定S区域的染色质可及性和组蛋白修饰调节类别开关重组的假设提供了证据。在AIM 1中，我们建议研究SUV39H1在内源开关重组及其功能机理中的作用。我们将研究SUV39H1抑制序列特异性DNA结合蛋白的活性以抑制开关重组对IgA的假设。该抑制蛋白的最有可能的候选者是LSF/CP-2/LBP-1C，已知该蛋白质结合组蛋白脱乙酰基酶和多染色体组蛋白。 AIM 2将是确定LSF是否专门抑制正常脾B细胞中的IgA转换重组，并检查LSF抑制IgA转换的机制。