Title:
Exonization of the LTR transposable elements in human genome
Exonization of the LTR transposable elements in human genome
Author(s)
Piriyapongsa, Jittima
Polavarapu, Nalini
Borodovsky, Mark
McDonald, John F.
Polavarapu, Nalini
Borodovsky, Mark
McDonald, John F.
Advisor(s)
Editor(s)
Collections
Supplementary to
Permanent Link
Abstract
Background: Retrotransposons have been shown to contribute to evolution of both structure
and regulation of protein coding genes. It has been postulated that the primary mechanism by which
retrotransposons contribute to structural gene evolution is through insertion into an intron or a
gene flanking region, and subsequent incorporation into an exon.
Results: We found that Long Terminal Repeat (LTR) retrotransposons are associated with 1,057
human genes (5.8%). In 256 cases LTR retrotransposons were observed in protein-coding regions,
while 50 distinct protein coding exons in 45 genes were comprised exclusively of LTR
RetroTransposon Sequence (LRTS). We go on to reconstruct the evolutionary history of an
alternatively spliced exon of the Interleukin 22 receptor, alpha 2 gene (IL22RA2) derived from a
sequence of retrotransposon of the Mammalian apparent LTR retrotransposons (MaLR) family.
Sequencing and analysis of the homologous regions of genomes of several primates indicate that
the LTR retrotransposon was inserted into the IL22RA2 gene at least prior to the divergence of
Apes and Old World monkeys from a common ancestor (~25 MYA). We hypothesize that the
recruitment of the part of LTR as a novel exon in great ape species occurred prior to the
divergence of orangutans and humans from a common ancestor (~14 MYA) as a result of a single
mutation in the proto-splice site.
Conclusion: Our analysis of LRTS exonization events has shown that the patterns of LRTS
distribution in human exons support the hypothesis that LRTS played a significant role in human
gene evolution by providing cis-regulatory sequences; direct incorporation of LTR sequences into
protein coding regions was observed less frequently. Combination of computational and
experimental approaches used for tracing the history of the LTR exonization process of IL22RA2
gene presents a promising strategy that could facilitate further studies of transposon initiated gene
evolution.
Sponsor
Date Issued
2007-08-28
Extent
Resource Type
Text
Resource Subtype
Article