Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia.
Gene. 2011 Jun 1;478(1-2):42-9. doi: 10.1016/j.gene.2011.01.014. Epub 2011 Jan 25.
The 2',5'-oligoadenylate synthetases (2-5A synthetases, OAS) form a family of proteins presented in many branches of Metazoa. The phylum Porifera (sponges) contains OAS proteins which are different from those in vertebrates and form a distinct OAS subfamily. In turn, OAS proteins from different genera of Demospongia show rather low similarities in their primary structures. To ascertain divergence of the OAS genes within a particular sponge genus, we identified the OAS genes from the marine sponge Geodia barretti and compared them with those from another member of the genus Geodia, Geodia cydonium. The identity and similarity of the OAS sequences found in G. barretti with those from G. cydonium were considerably higher than identities and similarities compared with those from other sponges, 75% and 85% versus 27-30% and 42-47%, respectively. We also established the presence of a transcriptionally active polymorphic OAS pseudogene in the genome of G. barretti. The transcripts of the OAS pseudogene(s) lack several internal exons encoding necessary motifs for OAS enzymatic activity. The maintenance and further diversification of OAS gene(s) and pseudogene(s) suggest the prevalence of gene duplication events over the loss of gene duplicates in Geodia genomes during the evolution.
2',5'-寡聚腺苷酸合成酶（2-5A 合成酶，OAS）构成了一个存在于许多后生动物分支中的蛋白质家族。多孔动物门（海绵动物）包含 OAS 蛋白，它们与脊椎动物的 OAS 蛋白不同，形成了一个独特的 OAS 亚家族。反过来，来自不同寻常海绵属的 OAS 蛋白在其一级结构上显示出相当低的相似性。为了确定特定海绵属内 OAS 基因的分化，我们从海洋海绵 Geodia barretti 中鉴定了 OAS 基因，并将其与属内的另一个成员 Geodia cydonium 进行了比较。在 G. barretti 中发现的 OAS 序列与 G. cydonium 的同一性和相似性明显高于与其他海绵的同一性和相似性，分别为 75%和 85%，而 27-30%和 42-47%。我们还在 G. barretti 的基因组中确定了一个转录活性的多态性 OAS 假基因的存在。OAS 假基因的转录本缺乏几个内部外显子，这些外显子编码 OAS 酶活性所必需的基序。OAS 基因和假基因的维持和进一步多样化表明，在 Geodia 基因组的进化过程中，基因重复事件的普遍性超过了基因重复的丢失。
