The genetic code is not frozen but still evolving, which can result in the acquisition of 'dialectal' codons that deviate from the universal genetic code. RNA modifications in the anticodon region of tRNAs play a critical role in establishing such non-universal genetic codes. In echinoderm mitochondria, the AAA codon specifies asparagine instead of lysine. By analyzing mitochondrial (mt-) tRNA^Lys isolated from the sea urchin (Mesocentrotus nudus), we discovered a novel modified nucleoside, hydroxy-N⁶-threonylcarbamoyladenosine (ht⁶A), 3′ adjacent to the anticodon (position 37). Biochemical analysis revealed that ht⁶A37 has the ability to prevent mt-tRNA^Lys from misreading AAA as lysine, thereby indicating that hydroxylation of N⁶-threonylcarbamoyladenosine (t⁶A) contributes to the establishment of the non-universal genetic code in echinoderm mitochondria.

中文翻译：

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保守的tRNA修饰的羟基化在棘皮动物线粒体中建立了非通用的遗传密码。

遗传密码不是冻结的，而是仍在进化中，这可能导致获得背离通用遗传密码的“方言”密码子。tRNA的反密码子区域中的RNA修饰在建立这种非通用遗传密码中起着至关重要的作用。在棘皮动物线粒体中，AAA密码子指定天冬酰胺而不是赖氨酸。通过分析从海胆（Mesocentrotus nudus）分离的线粒体（mt-）tRNA ^Lys，我们发现了一个新的修饰核苷，羟基-N ^6-苏氨酸氨基甲酰腺苷（ht ⁶ A），3'与反密码子相邻（位置37）。生化分析表明，ht ⁶ A37具有预防mt-tRNA ^Lys的能力这是因为将AAA误读为赖氨酸，从而表明N ^6-苏氨甲氨酰腺苷（t ⁶ A）的羟基化有助于在棘皮动物线粒体中建立非通用的遗传密码。