Jasinskas A, Kersulyte D, Langmore J, Steponaviciute D, Jasinskiene N, Gineitis A
Department of Developmental Biology, Institute of Biochemistry, Vilnius, Lithuania.
Biochim Biophys Acta. 1997 Mar 20;1351(1-2):168-80. doi: 10.1016/s0167-4781(96)00193-5.
Histone acetylation is an extremely complex, reversible and specific process. In order to evaluate the importance of this modification for gene expression during sea urchin development, acetyl group turnover of histone lysine residues was blocked by sodium butyrate. The continuous presence of 15 Mm sodium butyrate in the incubation medium from the onset of development blocked gastrulation and resulted in chromatin containing hyperacetylated histone molecules in amounts usually not found in nature. At the mesenchyme blastula stage, the expression of the early histone genes was shut off and the expression of the late genes was switched on both in control and sodium butyrate-treated embryos. Investigation of the early histone gene chromatin structure in butyrate-treated embryos revealed a random distribution of nucleosomes when the genes were transcriptionally active as compared to regular nucleosomal packaging when genes were inactive. These changes in chromatin structure during development mimicked the chromatin structural transition of the early histone genes in control embryos. In addition, the ability of heat shock genes to be induced at elevated temperature and repressed at normal temperature was unaffected in butyrate treatment of embryos. Finally, the developmental profiles of the cytoskeletal CyIIIa actin gene expression in control and butyrate-treated embryos were very similar. The data presented suggest that turnover of histone acetyl groups and the overall level of histone acetylation are not determining factors in the up and down regulation of a number of genes during early development of sea urchin.
组蛋白乙酰化是一个极其复杂、可逆且具有特异性的过程。为了评估这种修饰对海胆发育过程中基因表达的重要性，用丁酸钠阻断组蛋白赖氨酸残基的乙酰基周转。从发育开始起，在孵育培养基中持续存在15 mM丁酸钠会阻断原肠胚形成，并导致染色质中含有超乙酰化组蛋白分子，其含量通常在自然界中并不常见。在间充质囊胚阶段，对照胚胎和经丁酸钠处理的胚胎中早期组蛋白基因的表达均关闭，晚期基因的表达均开启。对经丁酸钠处理的胚胎中早期组蛋白基因染色质结构的研究表明，与基因无活性时规则的核小体包装相比，当基因转录活跃时核小体呈随机分布。发育过程中染色质结构的这些变化模仿了对照胚胎中早期组蛋白基因的染色质结构转变。此外，在胚胎的丁酸钠处理中，热休克基因在高温下被诱导并在常温下被抑制的能力不受影响。最后，对照胚胎和经丁酸钠处理的胚胎中细胞骨架肌动蛋白基因CyIIIa表达的发育谱非常相似。所呈现的数据表明，在海胆早期发育过程中，组蛋白乙酰基的周转和组蛋白乙酰化的总体水平不是许多基因上调和下调的决定因素。
