mRNA Retrotransposition Coupled with 5' Inversion as a Possible Source of New Genes
mRNA Retrotransposition Coupled with 5' Inversion as a Possible Source of New Genes
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DOI：
10.1093/molbev/msp050
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发表时间：
2009-06-01
影响因子：
10.7
通讯作者：
Okada, Norihiro
中科院分区：
文献类型：
--
作者：
Kojima, Kenji K.;Okada, Norihiro
人类长散布核元件 1 (L1) 占据了我们基因组的六分之一，并以多种方式对基因组进化做出了贡献。大约 10% 的人类 L1 拷贝由两个 L1 片段组成； 5' 片段和 3' 片段处于头对头（即 5' 倒置）方向。除了介导自身的逆转录转座之外，L1 还具有“反式”动员 mRNA 的能力，并且逆转录转座 mRNA 序列（逆转录）的数量估计> 6,000。在这项研究中，我们通过比较人类和黑猩猩的基因组，鉴定出了 48 个人类特异性的追溯和 95 个黑猩猩特异性的追溯。在这些逆转录中，有 12 个是 5' 倒置的。这些5'倒置逆转录的特征与5'倒置L1拷贝的特征相似，表明5'倒置是由相同的机制产生的。通过这些发现，我们检查了逆转录的 5' 倒置生成编码具有不同 N 末端的肽的新基因的可能性。我们鉴定了几个潜在的 5'-反向逆转录基因，包括胸腺生成素β (TMPO) 和真核翻译起始因子 3 亚基 5 (EIF3F) 的逆转录基因。最有趣的候选者是小核核糖核蛋白多肽 N (SNRPN) 的 5' 倒置逆转录。该逆转录在多个器官中以相反方向转录，具有多个转录变体，并编码含有源自 SNRPN N 末端部分的肽片段的蛋白质。我们的结果表明，mRNA 逆转座与 5' 倒位相结合可能是产生不同于亲本基因的新基因的机制。
Human long interspersed nuclear element-1 (L1) occupies one-sixth of our genome and has contributed to genome evolution in various ways. Approximately 10% of human L1 copies are composed of two L1 segments; the 5' segment and 3' segment are in head-to-head (i.e., 5'-inverted) orientation. Besides mediating their own retrotransposition, L1 has the ability to mobilize mRNA "in trans," and the number of retrotransposed mRNA sequences (retrocopies) is estimated to be > 6,000. In this study, we identified 48 human-specific retrocopies and 95 chimpanzee-specific retrocopies by comparing the human and chimpanzee genomes. Among these retrocopies, 12 were 5'-inverted. The characteristics of these 5'-inverted retrocopies were similar to those of 5'-inverted L1 copies, indicating that the 5' inversion is generated by the same mechanism. With these findings, we examined the possibility that 5' inversion of the retrocopy generates a new gene that codes for a peptide with a different N terminus. We identified several potential 5'-inverted retrogenes, including those of thymopoietin beta (TMPO) and eukaryotic translation initiation factor 3 subunit 5 (EIF3F). The most interesting candidate was the 5'-inverted retrocopy of small nuclear ribonucleoprotein polypeptide N (SNRPN). This retrocopy was transcribed in the reverse orientation in several organs, had multiple transcript variants, and encoded a protein containing a peptide fragment derived from the N-terminal portion of SNRPN. Our results suggest that mRNA retrotransposition coupled with 5' inversion may be a mechanism to generate new genes distinct from parental genes.