Template-dependent 3′-5′ nucleotide addition is a shared feature of tRNAHis guanylyltransferase enzymes from multiple domains of life
Template-dependent 3′-5′ nucleotide addition is a shared feature of tRNAHis guanylyltransferase enzymes from multiple domains of life
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DOI：
10.1073/pnas.0910961107
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发表时间：
2010-01-12
影响因子：
11.1
通讯作者：
Jackman, Jane E.
中科院分区：
文献类型：
--
作者：
Abad, Maria G.;Rao, Bhalchandra S.;Jackman, Jane E.
额外的5'鸟苷残基（G(-1)）的存在是tRNA（His）的独特特征。G（-1）在真核生物中通过tRNA（His）鸟苷转移酶（Thg1）催化的不寻常的3‘-5’核苷酸加成反应被转录后结合。酵母Thg1催化了意想不到的第二种活性：沃森-克里克依赖的3‘-5’核苷酸添加，与所有已知的DNA和RNA聚合酶的核苷酸添加方向相反。这一发现导致了一种假设，即Thg1家族成员可以利用这种不寻常的酶活性发挥其他作用。在这里，我们发现Thg1的古细菌同源物在体外和体内酵母中催化G（-1）添加，但仅在模板反应中，即与含有C-73鉴别核苷酸的tRNA（His）底物反应。由于来自古细菌的tRNA（His）含有C-73，这些发现与模板核苷酸添加在古细菌tRNA（His）成熟中的生理功能一致。此外，与酵母Thg1不同，古细菌Thg1酶也表现出对模板依赖性U-1添加到含有a（73）的tRNA（His）上的偏好。综上所述，这些结果表明，依赖于沃森-克里克模板的3‘-5’核苷酸加成是Thg1家族成员来自多个生命领域所表现出的共同催化活性，因此，这种不寻常的反应可能构成了Thg1酶家族最早成员的祖先活性。
The presence of an additional 5' guanosine residue (G(-1)) is a unique feature of tRNA(His). G(-1) is incorporated posttranscriptionally in eukarya via an unusual 3'-5' nucleotide addition reaction catalyzed by the tRNA(His) guanylyltransferase (Thg1). Yeast Thg1 catalyzes an unexpected second activity: Watson-Crick-dependent 3'-5' nucleotide addition that occurs in the opposite direction to nucleotide addition by all known DNA and RNA polymerases. This discovery led to the hypothesis that there are alternative roles for Thg1 family members that take advantage of this unusual enzymatic activity. Here we show that archaeal homologs of Thg1 catalyze G(-1) addition, in vitro and in vivo in yeast, but only in a templated reaction, i.e. with tRNA(His) substrates that contain a C-73 discriminator nucleotide. Because tRNA(His) from archaea contains C-73, these findings are consistent with a physiological function for templated nucleotide addition in archaeal tRNA(His) maturation. Moreover, unlike yeast Thg1, archaeal Thg1 enzymes also exhibit a preference for template-dependent U-1 addition to A(73)-containing tRNA(His). Taken together, these results demonstrate that Watson-Crick template-dependent 3'-5' nucleotide addition is a shared catalytic activity exhibited by Thg1 family members from multiple domains of life, and therefore, that this unusual reaction may constitute an ancestral activity present in the earliest members of the Thg1 enzyme family.