DNA SEQUENCES INVOLVED IN THE HEAVY CHAIN SWITCH

在免疫反应的早期，主要的免疫球蛋白重链 产生的免疫球蛋白是mu，后来在免疫反应中， 重链是γ、α或β。 这种重链使用的变化 是通过DNA重排完成的， 区域基因从μ恒定区到α恒定区， 恒定区，或四个γ 1，γ 2b， γ 2a或小鼠中的γ 3）恒定区。 这种DNA重排 涉及每个常数上游的DNA片段（称为开关片段） 区域基因 产生免疫球蛋白的细胞有六种不同的选择， 交换机重排。 这是一个重要的选择;七 不同的重链恒定区介导非常不同的效应子 功能，从而处理感染性生物体或其有毒产物， 非常不同的方式。 以前的研究结果表明，这种选择 在免疫球蛋白产生细胞中不是随机的，而是 监管. 此外，该调节似乎是由以下因素介导的： 特定开关区域染色质局部结构的变化。 所提议的实验的总体目标是了解分子 开关重组在基因特异性 路上了 我们计划鉴定可能控制重链的核蛋白 基因特异性重排，并确定DNA序列，他们 这家公司进退两难. 将测试候选调控DNA序列的 改变染色质/DNA结构的能力， 由DNA序列介导的转录。 DNA序列将会 通过瞬时转染产生和不产生 免疫球蛋白，并通过瞬时转染将被处理的细胞， 以各种方式诱导基因特异性重组。 我们将测试 相同序列调节DNA分子转录的能力 植入转基因小鼠体内。 最后，我们将尝试测试 序列调节从DNA的开关重组的能力 分子引入转基因小鼠。 我们将研究两个小鼠重 链基因，γ 1和γ 2a，以及两个开关重组的诱导物， γ 1用IL 4，γ 2a用干扰素γ。

Early in an immune response, the predominant immunoglobulin heavy chain produced is mu, later in the immune response the predominant immunoglobulin heavy chain is gamma, alpha, or epsilon. This change in heavy chain usage is accomplished by a DNA rearrangement that moves the heavy chain variable region gene from the mu constant region to the alpha constant region, epsilon constant region, or to one of the four gamma gamma1, gamma2b, gamma2a, or gamma3 in mouse) constant regions. This DNA rearrangement involves segments of DNA (called switch segments) upstream of each constant region gene. Immunoglobulin producing cells have a choice of six different switch rearrangements. This choice is an important one; the seven different heavy chain constant regions mediate very different effector functions and so handle an infectious organism or its toxic products in very different ways. Previous results have demonstrated that this choice is not random in the immunoglobulin producing cell, but rather is regulated. Furthermore, it seems likely that the regulation is mediated by changes in the local structure of chromatin of specific switch regions. The overall goal of the proposed experiments is to understand the molecular mechanisms by which switch recombination is regulated in a gene specific way. We plan to identify nuclear proteins that might control heavy chain gene-specific rearrangement and to identify the DNA sequences to which they bind. The candidate regulatory DNA sequences will be tested for their ability to alter chromatin/DNA structure by measuring changes in transcription mediated by the DNA sequences. The DNA sequences will be tested by transient transfection of cells that produce and do not produce immunoglobulin, and by transient transfection of cells that will be treated in various ways to induce gene-specific recombination. We will test the ability of the same sequences to regulate transcription from DNA molecules inserted into transgenic mice. Finally, we will attempt to test the ability of the sequences to regulate switch recombination from DNA molecules introduced into transgenic mice. We will study two murine heavy chain genes, gamma1 and gamma2a, and two inducers of switch recombination, IL4 for gamma1 and interferon-gamma for gamma2a.