DNA METHYLATION IN LYMPHOCYTES

已经提出了各种作用的甲基化和去甲基化的 真核DNA中的胞嘧啶。 这些可能的作用包括：（1）a 转录控制机制，（2）保护的修饰系统 （3）特定DNA片段的破坏，（3）维持或丢失 转化和非转化细胞中病毒基因组的潜伏状态， （4）控制DNA合成的起始。 的具体情况是 嗜淋巴细胞疱疹病毒，其中许多产生肿瘤的 淋巴系统中的各种动物，证据已经积累显示， DNA甲基化/去甲基化是变化的关键组成部分 病毒生命周期的潜伏期和繁殖期之间的联系 在这里提出的工作中，转化的淋巴细胞感染了 疱疹病毒Epstein-Barr将是一个实验系统， 确定DNA甲基化和去甲基化的机制。 两种病毒 从这些细胞系中分离的细胞DNA显示出高度可变的 在许多CG位点的甲基化程度。 我们在此建议， 分离并纯化甲基化酶（DNA甲基转移酶 淋巴细胞和测试可能的序列偏好，可变亲和力 病毒和细胞DNA，以及这些活动是否由病毒诱导 或者压抑 我们进一步建议开发三个独立的分析系统 以确定在这些细胞内运作的DNA去甲基化机制。

Various roles have been proposed for the methylation and demethylation of cytosines in eucaryotic DNA. These possible roles include: (1) a transcriptional control mechanism, (2) a modification system that protects specific pieces of DNA from destruction, (3) maintenance or loss of the latent state of viral genomes in both transformed and nontransformed cells, and (4) control of initiation of DNA synthesis. In the specific case of the lymphotropic herpesviruses, many of which generate tumors of the lymphatic system in a variety of animals, evidence has accumulated showing DNA methylation/demethylation to be a critical component of the shifts between latent and productive phases of the viral life cycle. In the work proposed here, transformed lymphocytes infected with the herpesvirus Epstein-Barr will be the experimental system employed to determine the mechanism of DNA methylation and demethylation. Both viral and cellular DNA isolated from these cell lines show highly variable degrees of methylation at many CG sites. We propose here to identify, isolate and purify methylases (DNA methyl transferases) from these lymphocytes and test for possible sequence preferences, variable affinities for viral and cellular DNA, and whether such activities are virally induced or repressed. We further propose to develop three separate assay systems to identify the DNA demethylating mechanism(s) operating within these cells.