Harlow P, Nemer M
Institute for Cancer Research, Fox Chase Cancer Center, Philadelphia, PA 19111.
Genes Dev. 1987 Apr;1(2):147-60. doi: 10.1101/gad.1.2.147.
Four beta-tubulin mRNAs in the embryo of the sea urchin Strongylocentrotus purpuratus are transcribed from at least 3 of the 9-12 beta-tubulin genes. A beta 1 tubulin mRNA of 1.8 kb, transcribed from a unique beta 1 gene, is expressed with high specificity in the pluteus ectoderm. Another 1.8-kb mRNA, beta 2, and a 2.5-kb beta 3 mRNA are moderately ectoderm specific. In contrast, a 3.0-kb beta 4 mRNA is highly specific for the endomesoderm tissue fraction. Certain similarities in developmental and tissue-specific expression suggest that these beta-tubulin genes may be related in their mode of regulation to counterparts among the genes for actin, another cytoskeletal protein. Measurements of absolute amounts revealed a distinct developmental profile for each beta-tubulin mRNA. An increase in the total amount of beta-tubulin mRNA in the early blastula was correlated with an increase in transcription rate per nucleus; whereas, later in the mesenchyme blastula stage, the beta-tubulin mRNA level decreased sharply as the rate of beta-tubulin gene transcription on a per embryo basis remained constant. Thus, during development through the blastula stages, there was a switch to a predominantly posttranscriptional regulation of beta-tubulin mRNA expression, probably through a decrease in mRNA stability.
海胆紫海胆胚胎中的四种β-微管蛋白mRNA是由9 - 12个β-微管蛋白基因中的至少3个转录而来。一种1.8 kb的β1微管蛋白mRNA由一个独特的β1基因转录，在长腕幼虫外胚层中高度特异性表达。另一种1.8 kb的mRNA，β2，以及一种2.5 kb的β3 mRNA在外胚层中具有中等特异性。相比之下，一种3.0 kb的β4 mRNA在内胚层组织部分中具有高度特异性。发育和组织特异性表达方面的某些相似性表明，这些β-微管蛋白基因在调控模式上可能与另一种细胞骨架蛋白肌动蛋白的基因相对应物相关。绝对量的测量揭示了每种β-微管蛋白mRNA独特的发育谱。囊胚早期β-微管蛋白mRNA总量的增加与每个细胞核转录速率的增加相关；而在间充质囊胚后期，β-微管蛋白mRNA水平急剧下降，而每个胚胎的β-微管蛋白基因转录速率保持不变。因此，在囊胚阶段的发育过程中，β-微管蛋白mRNA表达主要转向转录后调控，可能是通过mRNA稳定性的降低实现的。
