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
http://www.biomedcentral.com/news/20040414/01

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