Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-742, Korea.
Nucleic Acids Res. 2010 Apr;38(6):2099-110. doi: 10.1093/nar/gkp1151. Epub 2009 Dec 29.
Tpa1 (for termination and polyadenylation) from Saccharomyces cerevisiae is a component of a messenger ribonucleoprotein (mRNP) complex at the 3' untranslated region of mRNAs. It comprises an N-terminal Fe(II)- and 2-oxoglutarate (2OG) dependent dioxygenase domain and a C-terminal domain. The N-terminal dioxygenase domain of a homologous Ofd1 protein from Schizosaccharomyces pombe was proposed to serve as an oxygen sensor that regulates the activity of the C-terminal degradation domain. Members of the Tpa1 family are also present in higher eukaryotes including humans. Here we report the crystal structure of S. cerevisiae Tpa1 as a representative member of the Tpa1 family. Structures have been determined as a binary complex with Fe(III) and as a ternary complex with Fe(III) and 2OG. The structures reveal that both domains of Tpa1 have the double-stranded beta-helix fold and are similar to prolyl 4-hydroxylases. However, the binding of Fe(III) and 2OG is observed in the N-terminal domain only. We also show that Tpa1 binds to poly(rA), suggesting its direct interaction with mRNA in the mRNP complex. The structural and functional data reported in this study support a role of the Tpa1 family as a hydroxylase in the mRNP complex and as an oxygen sensor.
酵母 Tpa1（终止和多聚腺苷酸化）是信使核糖核蛋白（mRNP）复合物在 mRNA 非翻译区的一个组成部分。它包含一个 N 端 Fe(II)-和 2-氧戊二酸（2OG）依赖性双氧酶结构域和一个 C 端结构域。来自酿酒酵母的同源 Ofd1 蛋白的 N 端双氧酶结构域被认为作为一个氧传感器，调节 C 端降解结构域的活性。Tpa1 家族的成员也存在于真核生物中，包括人类。在这里，我们报告了酿酒酵母 Tpa1 的晶体结构，作为 Tpa1 家族的一个代表性成员。结构已被确定为与 Fe(III)的二元复合物和与 Fe(III)和 2OG 的三元复合物。这些结构表明，Tpa1 的两个结构域都具有双链β-螺旋折叠结构，与脯氨酰 4-羟化酶相似。然而，只有在 N 端结构域中观察到 Fe(III)和 2OG 的结合。我们还表明，Tpa1 与 poly(rA)结合，表明其在 mRNP 复合物中与 mRNA 的直接相互作用。本研究报告的结构和功能数据支持 Tpa1 家族作为 mRNP 复合物中的羟化酶和氧传感器的作用。
