REGULATION OF MHC CLASS II EXPRESSION IN TROPHOBLAST

滋养细胞中 MHC II 类表达的调节

• 批准号: 2827357
• 负责人: SHAWN P MURPHY
• 金额: $ 19.79万
• 依托单位: ROSWELL PARK CANCER INSTITUTE
• 依托单位国家: 美国
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-05-10 至 2002-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/2827357
• 关键词: DNA footprinting; MHC class II antigen; embryo /fetus tissue /cell culture; gel mobility shift assay; gene expression; gene induction /repression; genetic promoter element; genetic regulation; genetic regulatory element; genetic transcription; human tissue; immunofluorescence technique; nucleic acid sequence; polymerase chain reaction; pregnancy; transcription factor; transfection; trophoblast; western blottings

Trophoblast cells are unique because they do not express major histocompatibility complex (MHC) class II antigens under any known conditions. The absence of MHC class 11 antigens from the surface of trophoblast cells is thought to be critical for maintenance of the fetus during pregnancy. Thus, successful reproduction of mammals may require that MHC class II gene expression be stringently repressed in trophoblast cells. The regulation of class II antigen expression is mediated at the level of transcription in trophoblast cell lines from species with hemochorial placentas. Mutation analysis of the mouse IAalpha promoter resulted in the identification of a novel trophoblast-specific negative regulatory element (IAalphaNRE) that functions to repress class II transcription. Subsequent work demonstrated that human, mouse and rat trophoblast cell lines all lack the class II transactivator (CIITA), a transacting transcription factor that is essential for both constitutive and IFNgamma-inducible transcription in other cell types. Transfection of human and rat trophoblast cells with CIITA expression vectors resulted in cell surface class II antigen expression. Based on these data, my working hypothesis is that expression of the class II genes may be regulated by two complementary mechanism(s) in trophoblast cells: 1) repression of CIITA synthesis, and 2) the activity of negative regulatory elements in the promoters of class II genes. Furthermore, I propose that CIITA gene transcription may be repressed in trophoblast cells by cis-acting sequences that function only in trophoblast and early embryonic cells. The specific aims of this, my first application, are to: 1) identify the cis-acting DNA sequences and transacting factors required for repression of CIITA gene transcription in trophoblast and embryonal carcinoma (EC) cells; 2) determine the mechanism by which the IAalphaNREs function to repress class II gene transcription in trophoblast cells; and 3) examine the expression of the transcription factors that regulate CIITA gene transcription in fresh human trophoblast. These studies will provide the first step in understanding the biological consequences of trophoblastic expression of class II antigens to successful pregnancy.

滋养细胞是独特的，因为它们在任何已知条件下都不表达主要组织相容性复合体（MHC） II类抗原。滋养细胞表面MHC 11类抗原的缺失被认为对妊娠期间胎儿的维持至关重要。因此，哺乳动物的成功繁殖可能需要在滋养细胞中严格抑制MHC II类基因的表达。II类抗原表达的调控是在有胎盘的物种滋养细胞中通过转录水平介导的。对小鼠IAalpha启动子的突变分析导致鉴定出一种新的滋养细胞特异性负调控元件（IAalphaNRE），其功能是抑制II类转录。随后的研究表明，人类、小鼠和大鼠滋养细胞系都缺乏II类反激活因子（CIITA），这是一种转录因子，对于其他细胞类型的构成型和ifγ诱导型转录都是必不可少的。用CIITA表达载体转染人和大鼠滋养细胞，可在细胞表面表达II类抗原。基于这些数据，我的工作假设是，在滋养细胞中，II类基因的表达可能受到两种互补机制的调控：1)抑制CIITA合成，2)II类基因启动子中负调控元件的活性。此外，我提出CIITA基因转录可能在滋养层细胞中被仅在滋养层细胞和早期胚胎细胞中起作用的顺式作用序列所抑制。我的第一个应用程序的具体目的是：1)鉴定滋养细胞和胚胎癌（EC）细胞中抑制CIITA基因转录所需的顺式作用DNA序列和交易因子；2)确定IAalphaNREs抑制滋养细胞II类基因转录的机制；3)检测新鲜人滋养细胞中调控CIITA基因转录的转录因子的表达。这些研究将为理解滋养细胞表达II类抗原对成功妊娠的生物学影响提供第一步。