Kubiak Magdalena Regina, Makałowska Izabela
Department of Integrative Genomics, Institute of Anthropology, Faculty of Biology, Adam Mickiewicz University in Poznan, 61-614 Poznan, Poland.
Viruses. 2017 Apr 13;9(4):80. doi: 10.3390/v9040080.
Transposable elements, often considered to be not important for survival, significantly contribute to the evolution of transcriptomes, promoters, and proteomes. Reverse transcriptase, encoded by some transposable elements, can be used in to produce a DNA copy of any RNA molecule in the cell. The retrotransposition of protein-coding genes requires the presence of reverse transcriptase, which could be delivered by either non-long terminal repeat (non-LTR) or LTR transposons. The majority of these copies are in a state of "relaxed" selection and remain "dormant" because they are lacking regulatory regions; however, many become functional. In the course of evolution, they may undergo subfunctionalization, neofunctionalization, or replace their progenitors. Functional retrocopies (retrogenes) can encode proteins, novel or similar to those encoded by their progenitors, can be used as alternative exons or create chimeric transcripts, and can also be involved in transcriptional interference and participate in the epigenetic regulation of parental gene expression. They can also act in as natural antisense transcripts, microRNA (miRNA) sponges, or a source of various small RNAs. Moreover, many retrocopies of protein-coding genes are linked to human diseases, especially various types of cancer.
转座元件通常被认为对生存并不重要，但却对转录组、启动子和蛋白质组的进化有显著贡献。一些转座元件编码的逆转录酶可用于生成细胞中任何RNA分子的DNA拷贝。蛋白质编码基因的逆转座需要逆转录酶的存在，它可以由非长末端重复序列（non-LTR）或长末端重复序列（LTR）转座子传递。这些拷贝中的大多数处于“宽松”选择状态并保持“休眠”，因为它们缺乏调控区域；然而，许多拷贝会变得具有功能。在进化过程中，它们可能会经历亚功能化、新功能化或取代其祖先基因。功能性逆转录拷贝（逆转录基因）可以编码蛋白质，这些蛋白质与它们祖先基因编码的蛋白质相似或不同，可以用作替代外显子或产生嵌合转录本，还可以参与转录干扰并参与亲本基因表达的表观遗传调控。它们还可以作为天然反义转录本、微小RNA（miRNA）海绵或各种小RNA的来源发挥作用。此外，许多蛋白质编码基因的逆转录拷贝与人类疾病有关，尤其是各种类型的癌症。
