Hickey R J, Boshar M F, Crain W R
Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.
Dev Biol. 1987 Nov;124(1):215-27. doi: 10.1016/0012-1606(87)90473-8.
The relative transcription of three unlinked actin genes of the sea urchin Strongylocentrotus purpuratus was measured in isolated nuclei, at several stages during embryonic development. Transcription of two cytoskeletal actin genes, CyI and CyIIIa, was first detected in 64-128 cell embryos. At the early stages, the CyIIIa gene is several-fold more active per embryo than CyI. The relative transcription of these two genes changes as development proceeds so that by the pluteus stage the CyI gene is at least twice as active per embryo as the CyIIIa gene. Both the time of initial detection of transcription of these two genes and the shift in their relative transcription during development correspond closely with the appearance and relative abundance in embryos of the mRNAs from these genes. Transcription of the muscle actin gene M was first detected in nuclei from pluteus stage embryos and thus also closely correlates with the first appearance of the muscle actin gene mRNA in embryos. The tight temporal coupling of the appearance in embryos of mRNA from these genes and the detection of their transcription in nuclei suggests that the regulation of their expression is in large part transcriptional. In addition to examining the transcription of these actin genes, we discovered that a member of an actively transcribed repeated sequence family is located upstream of the muscle actin-coding sequence. This sequence, which is present at least several hundred times within the genome and hybridizes strongly to RNA synthesized by RNA polymerase III at cleavage stages and to RNA synthesized in nuclei from pluteus stage embryos, shows little hybridization at blastula and gastrula stages.
在胚胎发育的几个阶段，对紫海胆（Strongylocentrotus purpuratus）三个不连锁的肌动蛋白基因的相对转录进行了分离细胞核中的测量。两个细胞骨架肌动蛋白基因CyI和CyIIIa的转录首先在64 - 128细胞胚胎中被检测到。在早期阶段，每个胚胎中CyIIIa基因的活性比CyI高几倍。随着发育的进行，这两个基因的相对转录发生变化，以至于到长腕幼虫阶段，每个胚胎中CyI基因的活性至少是CyIIIa基因的两倍。这两个基因转录的初始检测时间以及它们在发育过程中相对转录的变化，都与这些基因的mRNA在胚胎中的出现和相对丰度密切相关。肌肉肌动蛋白基因M的转录首先在长腕幼虫阶段胚胎的细胞核中被检测到，因此也与肌肉肌动蛋白基因mRNA在胚胎中的首次出现密切相关。这些基因的mRNA在胚胎中的出现与它们在细胞核中转录的检测之间紧密的时间耦合表明，它们表达的调控在很大程度上是转录水平的。除了研究这些肌动蛋白基因的转录外，我们还发现一个活跃转录的重复序列家族的成员位于肌肉肌动蛋白编码序列的上游。该序列在基因组中至少存在数百次，在卵裂阶段与RNA聚合酶III合成的RNA强烈杂交，在长腕幼虫阶段胚胎的细胞核中合成的RNA也能与之强烈杂交，但在囊胚和原肠胚阶段几乎没有杂交信号。
