Chipev C C, Wolffe A P
Laboratory of Molecular Embryology, National Institute of Child Health and Human Development, Bethesda, Maryland 20892.
Mol Cell Biol. 1992 Jan;12(1):45-55. doi: 10.1128/mcb.12.1.45-55.1992.
We describe the chromosomal organization of the major oocyte and somatic 5S RNA genes of Xenopus laevis in chromatin isolated from erythrocyte nuclei. Both major oocyte and somatic 5S DNA repeats are associated with nucleosomes; however, differences exist in the organization of chromatin over the oocyte and somatic 5S RNA genes. The repressed oocyte 5S RNA gene is protected from nuclease digestion by incorporation into a nucleosome, and the entire oocyte 5S DNA repeat is assembled into a loosely positioned array of nucleosomes. In contrast, the potentially active somatic 5S RNA gene is accessible to nuclease digestion, and the majority of somatic 5S RNA genes appear not to be incorporated into positioned nucleosomes. Evidence is presented supporting the stable association of transcription factors with the somatic 5S RNA genes. Histone H1 is shown to have a role both in determining the organization of nucleosomes over the oocyte 5S DNA repeat and in repressing transcription of the oocyte 5S RNA genes.
我们描述了非洲爪蟾主要卵母细胞和体细胞5S RNA基因在从红细胞核分离出的染色质中的染色体组织情况。主要卵母细胞和体细胞5S DNA重复序列均与核小体相关；然而，卵母细胞和体细胞5S RNA基因上的染色质组织存在差异。受抑制的卵母细胞5S RNA基因通过整合到核小体中而免受核酸酶消化，并且整个卵母细胞5S DNA重复序列被组装成排列松散的核小体阵列。相比之下，具有潜在活性的体细胞5S RNA基因可被核酸酶消化，并且大多数体细胞5S RNA基因似乎未整合到定位的核小体中。文中提供的证据支持转录因子与体细胞5S RNA基因的稳定结合。已表明组蛋白H1在确定卵母细胞5S DNA重复序列上核小体的组织以及抑制卵母细胞5S RNA基因转录方面均发挥作用。
