Landes G M, Martinson H G
J Biol Chem. 1982 Sep 25;257(18):11002-7.
Chick embryo red blood cells express the embryonic globin and the rRNA genes before 5 days of development but only the adult globin genes and no rRNA after 12 days of development. We have isolated nuclei from the red blood cells of these developmental stages and allowed them to transcribe in vitro. We have analyzed the overall transcriptional properties of these nuclei, the overall activities of RNA polymerases I and II and the sequence-specific activity of RNA polymerase II in the beta-globin domain using cloned genomic hybridization probes. Among our findings are the following. 1) Erythroid nuclei of 5-day embryos are more transcriptionally active than those at 12 days. 2) RNA polymerase I is a very active at 5 days but is off by 12 days. 3) A template-independent activity which yields labeled RNA is present in the red cell nuclei of 12-day but not 5-day embryos. 4) Between 5 and 12 days of development transcriptional modulation delineates embryonic and adult beta-globin domains. 5) These domains exceed the boundaries of the genes themselves by several kilobases. 6) All transcripts which hybridize to sequences in the beta-globin gene region, including repeat sequence transcripts, are transcribed by RNA polymerase II.
鸡胚红细胞在发育5天前表达胚胎型珠蛋白和rRNA基因，但在发育12天后只表达成体型珠蛋白基因，且不表达rRNA。我们从这些发育阶段的红细胞中分离出细胞核，并让它们在体外进行转录。我们使用克隆的基因组杂交探针分析了这些细胞核的整体转录特性、RNA聚合酶I和II的整体活性以及RNA聚合酶II在β-珠蛋白结构域中的序列特异性活性。我们的发现如下：1）5天胚胎的红细胞核转录活性比12天胚胎的红细胞核高。2）RNA聚合酶I在5天时非常活跃，但在12天时失活。3）一种产生标记RNA的模板非依赖性活性存在于12天胚胎的红细胞核中，而5天胚胎的红细胞核中不存在。4）在发育的5天到12天之间，转录调控划定了胚胎型和成人型β-珠蛋白结构域。5）这些结构域超出了基因本身的边界达几千个碱基对。6）所有与β-珠蛋白基因区域序列杂交的转录本，包括重复序列转录本，均由RNA聚合酶II转录。
