Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, Kentucky 40536, USA.
Reproduction. 2009 Jun;137(6):923-9. doi: 10.1530/REP-09-0015. Epub 2009 Mar 31.
The Hspa1b (Hsp70.1) gene is one of the first genes expressed after fertilization, with expression occurring during the minor zygotic genome activation (ZGA) in the absence of stress. This expression can take place in the male pronucleus as early as the one-cell stage of embryogenesis. The importance of HSPA1B for embryonic viability during times of stress is supported by studies showing that depletion of this protein results in a significant reduction in embryos developing to the blastocyte stage. Recently, we have begun addressing the mechanism responsible for allowing expression of Hspa1b during the minor ZGA and found that heat shock transcription factor (HSF) 1 and 2 bind the Hspa1b promoter during late spermatogenesis. In this report, we have extended those studies using western blots and chromatin immunoprecipitation assays and found that RNA polymerase II (Pol II) is present in epididymal spermatozoa and bound to the Hspa1b promoter. These present results, in addition to our previous results, support a model in which the binding of HSF1, HSF2, SP1, and Pol II to the promoter of Hspa1b would allow the rapid formation of a transcription-competent state during the minor ZGA, thereby allowing Hspa1b expression.
Hspa1b（Hsp70.1）基因是受精后最早表达的基因之一，在没有应激的情况下，其表达发生在微小的合子基因组激活（ZGA）期间。这种表达早在胚胎发生的单细胞阶段就可以在雄性原核中进行。在应激时期，HSPA1B 对胚胎存活的重要性得到了研究的支持，这些研究表明，这种蛋白质的耗竭会导致发育到胚泡阶段的胚胎数量显著减少。最近，我们开始研究允许在微小的 ZGA 期间表达 Hspa1b 的机制，并发现热休克转录因子（HSF）1 和 2 在晚期精子发生期间结合 Hspa1b 启动子。在本报告中，我们使用 Western blot 和染色质免疫沉淀分析扩展了这些研究，并发现 RNA 聚合酶 II（Pol II）存在于附睾精子中，并与 Hspa1b 启动子结合。这些现有结果，以及我们之前的结果，支持了这样一种模型，即 HSF1、HSF2、SP1 和 Pol II 与 Hspa1b 启动子的结合将允许在微小的 ZGA 期间快速形成转录活性状态，从而允许 Hspa1b 表达。
