Evolution of the Antisense Overlap between Genes for Thyroid Hormone Receptor and Rev-erbα and Characterization of an Exonic G-Rich Element That Regulates Splicing of TRα2 mRNA.
Evolution of the Antisense Overlap between Genes for Thyroid Hormone Receptor and Rev-erbα and Characterization of an Exonic G-Rich Element That Regulates Splicing of TRα2 mRNA.
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DOI：
10.1371/journal.pone.0137893
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发表时间：
2015
期刊：
影响因子：
3.7
通讯作者：
Waters PD
中科院分区：
文献类型：
--
作者：
Munroe SH;Morales CH;Duyck TH;Waters PD
α-甲状腺激素受体基因（TRα）编码两种功能不同的蛋白质：TRα1，α-甲状腺激素受体;和TRα2，非激素结合变体。TRα2 mRNA的最后一个外显子与Rev-erbα mRNA的3'端重叠，后者编码另一个位于DNA相对链上的核受体。为了了解这种反义重叠的进化，我们对鸭嘴兽Orthorhynchus anatinus中的这些基因和mRNA进行了测序。尽管鸭嘴兽TRα/Rev-erbα基因座与其他哺乳动物有很强的同源性，但它缺乏表达TRα2所必需的元件。比较分析表明，TRα2 mRNA表达的选择性剪接在真兽目和有袋目哺乳动物分化之前以逐步的方式进化。位于TRα2 mRNA选择性3 '剪接位点下游的一个短的富含G的元件（G30）与Rev erb α的3' UTR反义，在调节TRα2剪接中起重要作用。G30在真兽目哺乳动物中高度保守，但在有袋类和单孔目动物中不存在。G30内的系统性缺失和替换对TRα2剪接具有显著不同的影响，导致其抑制或增强。破坏一个或多个G残基簇的突变会增强剪接两到三倍。这些结果表明，G30序列可以采用高度结构化的构象，可能是一个G-四链体，它是一个复杂的剪接调控元件的一部分，对TRα2表达产生积极和消极的影响。由于强烈增强体内剪接的突变对体外剪接没有影响，因此G30的调节作用很可能是通过转录和剪接的连锁介导的。
The α-thyroid hormone receptor gene (TRα) codes for two functionally distinct proteins: TRα1, the α-thyroid hormone receptor; and TRα2, a non-hormone-binding variant. The final exon of TRα2 mRNA overlaps the 3’ end of Rev-erbα mRNA, which encodes another nuclear receptor on the opposite strand of DNA. To understand the evolution of this antisense overlap, we sequenced these genes and mRNAs in the platypus Orthorhynchus anatinus. Despite its strong homology with other mammals, the platypus TRα/Rev-erbα locus lacks elements essential for expression of TRα2. Comparative analysis suggests that alternative splicing of TRα2 mRNA expression evolved in a stepwise fashion before the divergence of eutherian and marsupial mammals. A short G-rich element (G30) located downstream of the alternative 3’splice site of TRα2 mRNA and antisense to the 3’UTR of Rev-erbα plays an important role in regulating TRα2 splicing. G30 is tightly conserved in eutherian mammals, but is absent in marsupials and monotremes. Systematic deletions and substitutions within G30 have dramatically different effects on TRα2 splicing, leading to either its inhibition or its enhancement. Mutations that disrupt one or more clusters of G residues enhance splicing two- to three-fold. These results suggest the G30 sequence can adopt a highly structured conformation, possibly a G-quadruplex, and that it is part of a complex splicing regulatory element which exerts both positive and negative effects on TRα2 expression. Since mutations that strongly enhance splicing in vivo have no effect on splicing in vitro, it is likely that the regulatory role of G30 is mediated through linkage of transcription and splicing.