Rashbass J, Taylor M V, Gurdon J B
Wellcome/CRC Institute of Cancer & Developmental Biology, Cambridge, UK.
EMBO J. 1992 Aug;11(8):2981-90. doi: 10.1002/j.1460-2075.1992.tb05368.x.
Two alternatively spliced products of the human E2A gene, E12 and E47, encode helix-loop-helix DNA-binding proteins. Here we describe the isolation of two Xenopus cDNAs; one, XE12, is structurally similar to human E12 and the other contains a sequence similar to E47. Transcripts of both cDNAs are present at all the stages of Xenopus development tested and in all regions of the embryo. The DNA binding properties of in vitro translated XE12 are indistinguishable from those of human E12. We have shown previously that an embryonic muscle DNA-binding activity, EMF1, that binds to a promoter sequence required for the expression of the cardiac actin gene, contains the Xenopus myogenic factor XMyoD. Here we show that it also contains protein that interacts with an anti-E12 antiserum, suggesting that XE12 and XMyoD proteins, or very similar ones, are present in EMF1. We have addressed the functional role of XE12 in muscle gene transcription in Xenopus embryos by injecting in vitro synthesized RNA into the two cell embryo. Overexpression of XE12 and XMyoD augments by greater than 10-fold the ectopic activation of the endogenous cardiac actin gene that can be produced by XMyoD alone. Our DNA binding results strongly suggest that this effect is mediated through a direct interaction of the XE12-XMyoD complex with specific sites in the cardiac actin promoter. We suggest that XE12 is functionally important in muscle gene activation in embryonic development.
人类E2A基因的两种可变剪接产物E12和E47编码螺旋-环-螺旋DNA结合蛋白。在此，我们描述了两个非洲爪蟾cDNA的分离；一个是XE12，其结构与人类E12相似，另一个包含与E47相似的序列。这两种cDNA的转录本在所有测试的非洲爪蟾发育阶段以及胚胎的所有区域均有表达。体外翻译的XE12的DNA结合特性与人类E12的无法区分。我们之前已经表明，一种与心肌动蛋白基因表达所需启动子序列结合的胚胎肌肉DNA结合活性EMF1包含非洲爪蟾生肌因子XMyoD。在此我们表明，它还包含与抗E12抗血清相互作用的蛋白质，这表明EMF1中存在XE12和XMyoD蛋白，或者非常相似的蛋白。我们通过将体外合成的RNA注射到二细胞胚胎中来研究XE12在非洲爪蟾胚胎肌肉基因转录中的功能作用。XE12和XMyoD的过表达使仅由XMyoD产生的内源性心肌动蛋白基因的异位激活增加了10倍以上。我们的DNA结合结果强烈表明，这种效应是通过XE12 - XMyoD复合物与心肌动蛋白启动子中的特定位点直接相互作用介导的。我们认为XE12在胚胎发育过程中的肌肉基因激活中具有重要功能。
