Abe Ken-Ichiro, Yamamoto Ryoma, Franke Vedran, Cao Minjun, Suzuki Yutaka, Suzuki Masataka G, Vlahovicek Kristian, Svoboda Petr, Schultz Richard M, Aoki Fugaku
Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Japan.
Bioinformatics Group, Division of Biology, Faculty of Science, Zagreb University, Zagreb, Croatia.
EMBO J. 2015 Jun 3;34(11):1523-37. doi: 10.15252/embj.201490648. Epub 2015 Apr 20.
Initiation of zygotic transcription in mammals is poorly understood. In mice, zygotic transcription is first detected shortly after pronucleus formation in 1-cell embryos, but the identity of the transcribed loci and mechanisms regulating their expression are not known. Using total RNA-Seq, we have found that transcription in 1-cell embryos is highly promiscuous, such that intergenic regions are extensively expressed and thousands of genes are transcribed at comparably low levels. Striking is that transcription can occur in the absence of defined core-promoter elements. Furthermore, accumulation of translatable zygotic mRNAs is minimal in 1-cell embryos because of inefficient splicing and 3' processing of nascent transcripts. These findings provide novel insights into regulation of gene expression in 1-cell mouse embryos that may confer a protective mechanism against precocious gene expression that is the product of a relaxed chromatin structure present in 1-cell embryos. The results also suggest that the first zygotic transcription itself is an active component of chromatin remodeling in 1-cell embryos.
哺乳动物中合子转录的起始过程尚不清楚。在小鼠中，合子转录最早在1细胞胚胎原核形成后不久被检测到，但转录位点的身份以及调节其表达的机制尚不清楚。通过全RNA测序，我们发现1细胞胚胎中的转录非常杂乱，基因间区域广泛表达，数千个基因以相对较低的水平转录。引人注目的是，转录可以在没有明确的核心启动子元件的情况下发生。此外，由于新生转录本的剪接效率低下和3'加工过程，1细胞胚胎中可翻译的合子mRNA积累极少。这些发现为1细胞小鼠胚胎中的基因表达调控提供了新的见解，这可能赋予一种针对早熟基因表达的保护机制，而早熟基因表达是1细胞胚胎中存在的松弛染色质结构的产物。结果还表明，首次合子转录本身是1细胞胚胎中染色质重塑的一个活跃组成部分。
