| Cover Legend: The Philippine tarsier (Tarsius syrichta).
Tarsiers belong to a primate lineage that lacks the chimeric SETMAR
gene. The SETMAR gene arose 40-58 million years ago in the human
primate lineage by the capture of the transposase gene from a selfish mobile
element. Image courtesy of Katherine Gardner.
Abstract
The emergence of new genes and functions is of central importance to
the evolution of species. The contribution of various types of duplications
to genetic innovation has been extensively investigated. Less understood
is the creation of new genes by recycling of coding material from selfish
mobile genetic elements. To investigate this process, we reconstructed
the evolutionary history of SETMAR, a new primate chimeric gene
resulting from fusion of a SET histone methyltransferase gene
to the transposase gene of a mobile element. We show that the transposase
gene was recruited as part of SETMAR 40–58 million years
ago, after the insertion of an Hsmar1 transposon downstream of
a preexisting SET gene, followed by the de novo exonization
of previously noncoding sequence and the creation of a new intron. The
original structure of the fusion gene is conserved in all anthropoid lineages,
but only the N-terminal half of the transposase is evolving under strong
purifying selection. In vitro assays show that this region contains
a DNA-binding domain that has preserved its ancestral binding specificity
for a 19-bp motif located within the terminal-inverted repeats of Hsmar1
transposons and their derivatives. The presence of these transposons in
the human genome constitutes a potential reservoir of ~1,500 perfect or
nearly perfect SETMAR-binding sites. Our results not only provide
insight into the conditions required for a successful gene fusion, but
they also suggest a mechanism by which the circuitry underlying complex
regulatory networks may be rapidly established.
Ref: Cordaux, R., S. Udit, M. A. Batzer and C. Feschotte (2006) Birth of a chimeric primate
gene by capture of the transposase gene from a mobile element. Proceedings
of the National Academy of Sciences of the USA 103: 8101-8106 ( pdf )
Other links: This Week In PNAS Commentary
by King Jordan
Additional information about research projects in the Batzer lab is available
from the laboratory web site http://batzerlab.lsu.edu |
