Kondo M, Semba K, Shiokawa K, Yamamoto T
Department of Oncology, University of Tokyo, Japan.
Biochem Biophys Res Commun. 1996 Jan 17;218(2):549-55. doi: 10.1006/bbrc.1996.0098.
We cloned cDNAs coding for the Xenopus counterparts of a type I activin receptor. The cDNA clones were predicted to encode 56kd proteins, namely XAR3 and XAR4 proteins. The two proteins are highly homologous to each other, showing 96% identity in the amino acid sequences. The GST-fused kinase domain of XAR3 autophosphorylated itself in vitro on threonine residues. The expression of XAR4 was found throughout embryogenesis, from oocytes to tailbud embryos, and also in adult tissues. By whole mount in situ hybridization, the XAR4 transcripts were detected in the animal half of blastulae and dorsally in gastrulae and neurulae. In tadpoles, the transcript was seen in the brain and around the otic vesicles. These results show that the activin type I receptor is expressed during Xenopus embryogenesis and suggest that the type I and II receptors are expressed together both temporally and spatially, supporting the idea that activin induces mesoderm in the embryo through activation of the two types of receptors.
我们克隆了编码非洲爪蟾I型激活素受体对应物的cDNA。这些cDNA克隆预计编码56kd的蛋白质，即XAR3和XAR4蛋白。这两种蛋白质彼此高度同源，氨基酸序列的同一性为96%。XAR3的GST融合激酶结构域在体外自身的苏氨酸残基上发生自磷酸化。在整个胚胎发育过程中，从卵母细胞到尾芽胚胎，以及在成体组织中都发现了XAR4的表达。通过整体原位杂交，在囊胚的动物半球以及原肠胚和神经胚的背部检测到XAR4转录本。在蝌蚪中，转录本出现在大脑和耳泡周围。这些结果表明激活素I型受体在非洲爪蟾胚胎发育过程中表达，并表明I型和II型受体在时间和空间上共同表达，支持激活素通过激活这两种类型的受体在胚胎中诱导中胚层形成的观点。
