Martins Rui Pires, Krawetz Stephen A
Center for Molecular Medicine and Genetics, School of Medicine and Institute for Scientific Computing, Wayne State University, Detroit, MI 48201, USA.
Proc Natl Acad Sci U S A. 2007 May 15;104(20):8340-5. doi: 10.1073/pnas.0700076104. Epub 2007 May 1.
Potentiation is the transition from higher-order, transcriptionally silent chromatin to a less condensed state requisite to accommodating the molecular elements required for transcription. To examine the underlying mechanism of potentiation an approximately 13.7-kb mouse protamine domain of increased nuclease sensitivity flanked by 5' and 3' nuclear matrix attachment regions was defined. The potentiated DNase I-sensitive region is formed at the pachytene spermatocyte stage with the recruitment to the nuclear matrix of a large approximately 9.6-kb region just upstream of the domain. Attachment is then specified in the transcribing round spermatid, recapitulating the organization of the human cluster. In comparison to other modifiers that have no effect, i.e., histone methylation, HP1, and SATB1, topoisomerase engages nuclear matrix binding as minor marks of histone acetylation appear. Reorganization is marked by specific sites of topoisomerase II activity that are initially detected in leptotene-zygotene spermatocytes just preceding the formation of the DNase I-sensitive domain. This has provided a likely model of the events initiating potentiation, i.e., the opening of a chromatin domain.
增强作用是指从高阶转录沉默染色质转变为一种不太浓缩的状态，这种状态对于容纳转录所需的分子元件是必要的。为了研究增强作用的潜在机制，定义了一个约13.7 kb的小鼠鱼精蛋白结构域，其核酸酶敏感性增加，两侧为5'和3'核基质附着区域。增强的DNase I敏感区域在粗线期精母细胞阶段形成，该区域上游约9.6 kb的大片段区域被募集到核基质。然后在转录的圆形精子细胞中确定附着，重现人类簇的组织形式。与其他无作用的修饰因子（即组蛋白甲基化、HP1和SATB1）相比，随着组蛋白乙酰化的微小标记出现，拓扑异构酶参与核基质结合。重组以拓扑异构酶II活性的特定位点为标志，这些位点最初在DNase I敏感结构域形成之前的细线期-偶线期精母细胞中被检测到。这提供了一个启动增强作用事件的可能模型，即染色质结构域的开放。
