Contribution of Transposable Elements to Human Proteins

Abstract

More than half of the human genome originated in transposable elements (TEs). Although these segments are mostly located in intronic and intergenic regions, some of them can be found in protein‐coding exons. Moreover, some functionally important genes evolved from TEs. These genes are involved in major biological processes such as immunity, replication, reproduction, cell proliferation and apoptosis. In addition, TEs contribute to human proteome indirectly by retrocopying messenger ribonucleic acid (mRNA) molecules back to the genome and creating new variants of the existing genes, which in turn can evolve a new function or new expression pattern. This demonstrates the importance of TEs as a genomic pool of coding sequences for the creation and evolution of gene functions.

Key Concepts

  • More than half of the human genome originated in transposable elements and they have profound consequences for the genome evolution.
  • Transposable elements contribute to the human proteome either directly by co‐option of TE‐originated sequences or indirectly by using TE's molecular machinery to duplicate existing genetic material.
  • Retrogenes are byproducts of L1 element activity.
  • Human genes can be shuffled by the process called genome transduction that involves "leaking" transcription of a transposon.
  • Transposons moving around the genome can alter expression profile of the host genes.

Keywords: transposable elements; exaptation; human genome; molecular domestication; exonisation; gene evolution; retrogenes; alternative splicing; gene duplication

Figure 1. Structures of mobile elements present in the human genome. LTR, long terminal repeat; TSD, target site duplication; TIR, terminal inverted repeat and A and B, polymerase III internal promoters.
Figure 2. Evolutionary events leading to alternatively spliced TE cassette.
Figure 3. Simplified evolutionary history of human RNF113A gene. Shaded part of the RNF113B gene becomes an intron in one of the mRNA splicing variants.
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Makałowski, Wojciech, Kischka, Tabea, and Makałowska, Izabela(Apr 2017) Contribution of Transposable Elements to Human Proteins. In: eLS. John Wiley & Sons Ltd, Chichester. http://www.els.net [doi: 10.1002/9780470015902.a0020793.pub2]