CONTROL OF DEVELOPMENTAL GENE EXPRESSION--CHROMATIN STRUCTURE OF ACTIVE GENES

一个非常简单的模型系统，细胞黏液霉菌，网柄菌属 Discoideum，正被用来研究控制 发育基因在正常分化过程中的激活。在成长中 Dictyostelius细胞聚集的早期阶段表达50-55%的 它们的单拷贝基因组为信使核糖核酸和核糖核酸。另外26%的 单拷贝基因组只在病毒的晚期表达 发展。在基因组的晚期启动转录 所需的细胞间相互作用和cAMP。因为这么高的比例 这个小的真核基因组的组成要么被转录，要么 发展诱导，它提供了一个独特的机会来研究 转录活性基因染色质的结构组织。 我们的结果表明，无论是结构性表达还是 发育可诱导基因位于DNase I敏感的、活跃的 染色质中的结构无论发育是否可诱导 基因正在被转录。相比之下，微球菌核酸酶 用于识别基因特有的结构组织，这些基因 实际上正在被转录的过程中。此对象的属性 组织已经被用来特异性地拆分寡核小体 从活跃转录的基因中提取并确定它们的蛋白质 作曲。

A very simple model system, the cellular slime mold, Dictyostelium discoideum, is being used to study the mechanisms which control developmental gene activation during normal differentiation. During growth and the early stages of aggregation Dictyostelium cells express 50-55% of their single copy genome as mRNA and HnRNA. An additional 26% of the single copy genome is expressed only during the late stages of development. Initiation of transcription on the late portion of the genome required cell-cell intreraction and cAMP. Because such a high proportion of this small eukaryotic genome is either constitutively transcribed or developmentally induced, it offers a unique opportunity to study the structural organization in chromatin of transcriptionally active genes. Our results indicate that both the constitutively expressed and developmentally inducible genes are in a DNase I-sensitive, active structure in chromatin regardless of whether the developmentally inducible genes are being transcribed. By contrast, micrococcal nuclease has been used to identify a structural organization unique to genes which are actually in the process of being transcribed. Properties of this organization have been used to resolve oligonucleosomes specifically derived from actively transcribed genes and to determine their protein compostion.