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

一个非常简单的模型系统，细胞黏菌，网柄菌 discoideum，被用来研究控制 在正常分化过程中发育基因激活。 在生长期间 和聚集的早期阶段，网骨藻细胞表达50-55%的 它们的单拷贝基因组作为mRNA和HnRNA。 另外26%的 单拷贝基因组仅在发育的晚期表达， 发展 基因组晚期转录起始 需要细胞间相互作用和cAMP。 因为如此高的比例 这个小的真核基因组的组成性转录或 发展诱导，它提供了一个独特的机会，研究 转录活性基因染色质结构组织。 我们的研究结果表明，无论是组成型表达， 发育诱导基因在DNA酶I敏感的，活跃的 无论发育诱导的 基因正在被转录。 相比之下，微球菌核酸酶已经被 用于识别基因特有的结构组织， 实际上正在被转录。 合金性能都 组织已被用来解决寡核小体特异性 从活跃转录的基因中提取，并确定其蛋白质 组成。

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.