Huber M C, Krüger G, Bonifer C
Institut für Biologie 111 der Universität Freiburg, Germany.
Nucleic Acids Res. 1996 Apr 15;24(8):1443-52. doi: 10.1093/nar/24.8.1443.
The chicken lysozyme locus is gradually activated during macrophage development exhibiting a specific chromatin structure with each differentiation state. Its small size and the extensive characterization of its cis-regulatory elements allows us to study even subtle changes in chromatin structure of the entire gene locus during transcriptional activation. Tissue-specific and position independent expression of the lysozyme locus in transgenic mice requires the cooperation of all cis-regulatory elements. In order to elucidate further the molecular basis of locus activation, we have determined nucleosome positions within the complete 5'-regulatory region of the chicken lysozyme locus in chicken myeloid cell lines and transgenic mice. Each cis-regulatory element develops its unique nucleosomal structure and each one remodels chromatin differently. The nucleosomal organization of the endogenous gene in chicken cell lines and the transgene in the mouse turned out to be identical, enabling us to study the influence of cis-regulatory deletions on the development of an active chromatin structure in transgenic mice. Transgenes with a deletion of an important cis-regulatory element show an impediment in nucleosome reorganization as compared with the complete lysozyme locus. We demonstrate that multicopy transgene-clusters in position dependently expressing mouse lines exhibit a heterogeneous chromatin organization.
鸡溶菌酶基因座在巨噬细胞发育过程中逐渐被激活，在每个分化状态下都呈现出特定的染色质结构。其基因座较小，且对顺式调控元件有广泛的表征，这使我们能够研究转录激活过程中整个基因座染色质结构的细微变化。溶菌酶基因座在转基因小鼠中的组织特异性和位置独立性表达需要所有顺式调控元件的协同作用。为了进一步阐明基因座激活的分子基础，我们确定了鸡骨髓细胞系和转基因小鼠中鸡溶菌酶基因座完整5'调控区内的核小体位置。每个顺式调控元件都形成其独特的核小体结构，且每个元件对染色质的重塑方式不同。结果表明，鸡细胞系中的内源基因和小鼠中的转基因的核小体组织是相同的，这使我们能够研究顺式调控缺失对转基因小鼠中活性染色质结构发育的影响。与完整的溶菌酶基因座相比，缺失重要顺式调控元件的转基因在核小体重组方面存在障碍。我们证明，在位置依赖性表达的小鼠品系中，多拷贝转基因簇呈现出异质性染色质组织。
