Copies key for gene networks Majority of network evolution
appears to have occurred by duplication and divergence By
Cathy Holding
Although the understanding of gene regulation networks and
their importance has grown, how these complex pathways
evolved has been poorly understood. New research in the
April 11 Nature Genetics suggests that during evolution gene
duplication and subsequent divergence could have been
responsible for up to 90% of the interactions seen in gene
regulatory networks.
Sarah A. Teichmann and M. Madan Babu at the Medical Research
Council in Cambridge, UK, looked for homologous genes in
known genetic networks in Escherichia coli and Saccharomyces
cerevisiae to discover instances of duplication. Teichmann
said that their approach to identifying and quantifying
effects of duplication was different from previous attempts
in that they were looking at both transcription factors and
target genes together. They had captured both recent and
distant evolutionary relationships by using information
about structural domains in homologous genes, using a hidden
Markov model database called SUPERFAMILY.
"The general principle behind this is that structure changes
more slowly than sequence," Teichmann said. "Things can be
conserved at the level of three-dimensional structure,
whereas the amino acid sequence can be completely
different." By mapping domains of known structure onto
transcription factors and their target genes, a much more
complete picture of the evolutionary relationships of the
entire regulatory network was obtained, she said.
The authors' results indicated that the 90% observed
duplication of gene networking interactions could be further
broken down. Simple duplication while retaining the
interactions of the ancestor accounts for about 50% of
duplications, and the remaining half of duplication cases
involve inventing new interactions relative to their
ancestors. "When we say 90%. we're including those [new
interaction] cases, and that's not to be sniffed at either;
that occurs fairly frequently as well," Teichmann said.
Read the rest at The Scientist
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