Swaroop A, Agarwal N, Gruen J R, Bick D, Weissman S M
Department of Ophthalmology, University of Michigan, Kellogg Eye Center, Ann Arbor 48105.
Nucleic Acids Res. 1991 Sep 11;19(17):4725-9. doi: 10.1093/nar/19.17.4725.
The Gs alpha guanine nucleotide-binding signal transduction protein is part of a heterotrimeric complex that is involved in the stimulation of adenylate cyclase upon activation of membrane receptors. We report the characterization of 16 Gs alpha cDNA clones isolated from the human adult retina and fetal eye libraries. Molecular heterogeneity in the 5'-region defines four novel Gs alpha cDNA species which are generated either by alternate splicing or by using alternative promoter. The novel exons upstream of exon 2 interrupt the highly conserved 'region A' in the Gs alpha polypeptide. Non-AUG codons in the novel 5'-exon can initiate translation of these Gs alpha species in vitro. Reverse transcription of total RNA coupled with polymerase chain reaction (RTPCR) using specific primers and in situ hybridization to mRNA in baboon tissue sections with a specific oligonucleotide probe show a high level of expression of these species in retina and brain but not in liver. Differential expression of alternatively spliced Gs alpha species suggests novel signal transducing pathways.
Gsα鸟嘌呤核苷酸结合信号转导蛋白是异源三聚体复合物的一部分，该复合物在膜受体激活后参与刺激腺苷酸环化酶。我们报告了从成人视网膜和胎儿眼文库中分离出的16个Gsα cDNA克隆的特征。5'区域的分子异质性定义了四种新的Gsα cDNA种类，它们是通过可变剪接或使用替代启动子产生的。外显子2上游的新外显子打断了Gsα多肽中高度保守的“A区”。新5'外显子中的非AUG密码子可以在体外启动这些Gsα种类的翻译。使用特异性引物进行总RNA的逆转录与聚合酶链反应（RTPCR），并用特异性寡核苷酸探针与狒狒组织切片中的mRNA进行原位杂交，结果显示这些种类在视网膜和大脑中高表达，而在肝脏中不表达。可变剪接的Gsα种类的差异表达提示了新的信号转导途径。
