Newly evolved genes adopt a variety of strategies to remain in the gene pool

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Newly evolved genes adopt a variety of strategies to remain in the

gene pool

http://www.medicalnewstoday.com/medicalnews.php?newsid=31586

05 Oct 2005

When Mother Nature creates an identical copy of a gene in an

organism's genome, the duplicated copy is usually deleted,

inactivated, or otherwise rendered nonfunctional in order to prevent

genetic redundancy and to preserve biological homeostasis. In some

cases, however, gene duplicates are maintained in a functional state.

Until now, the biological and evolutionary forces behind the

maintenance of these duplicates as functional components of the

genome have remained unclear.

To determine the basis for the persistence of functional gene

duplicates in the genome, three scientists at the Institute of

Molecular Systems Biology at the Swiss Federal Institute of

Technology in Zürich have collaborated on the largest systematic

analysis of duplicated gene function to date. Using an integrative

combination of computational and experimental approaches, they

classified duplicate pairs of genes involved in yeast metabolism into

three functional categories: (1) back-up, where a duplicate gene copy

has acquired the ability to compensate in the absence of the other

copy, (2) subfunctionalization, where a duplicate copy has evolved a

completely new, non-overlapping function, (3) regulation, where the

differential regulation of duplicates fine-tunes pathway usage, and

(4) gene dosage, where the increased expression provided by the

duplicate gene copy augments production of the corresponding protein.

Their results, which appear in the October issue of the journal

Genome Research, indicate that no single role prevails but that all

four of the mechanisms play a substantial role in maintaining

duplicate genes in the genome.

" Our results contradict other recent publications that have focused

on a single selective pressure as the basis for the retention of gene

duplicates, " explains Dr. Uwe Sauer, principal investigator on the

project and Professor at the Institute of Molecular Systems Biology

at the Swiss Federal Institute of Technology in Zürich. " We show

that, at least for yeast metabolism, the persistence of the

duplicated fraction of the genome can be better explained with an

array of different, often overlapping functional roles. "

Yeast metabolism provides an ideal model for investigating the

functional basis for gene duplication because a large proportion of

genes involved in this biological process have been duplicated. Of

the 672 genes involved in yeast metabolism, 295 genes can be

classified into 105 families of duplicates. To put this into

perspective, the yeast genome has an estimated total of 6,000 genes,

1,500 of which are considered to be duplicates. An ancient whole-

genome duplication event is thought to be responsible for the

formation of many of these duplicate copies.

Sauer's group demonstrated that of the 105 families of duplicated

gene families involved in yeast metabolism, 34 demonstrated back-up

function, 19 were involved in increased gene dosage, 18 exhibited

regulatory functions, and 18 had evolved new, more specialized

functions. Therefore, each of these mechanisms plays a substantial

and important role in the maintenance of functional duplicates in the

gene pool.

This work will be published in the October print issue of Genome

Research and is available online at

genome.org/cgi/doi/10.1101/gr.3992505. Its citation is as follows:

Kuepfer, L., Sauer, U. and Blank, L.M. 2005. Metabolic functions of

duplicate genes in Saccharomyces cerevisiae. Genome Res. 15: 1421-

1430.

Genome Research (www.genome.org) is an international, monthly, peer-

reviewed journal published by Cold Spring Harbor Laboratory Press.

Launched in 1995, it is one of the five most highly cited primary

research journals in genetics and genomics. The journal publishes

novel genome-based studies and cutting-edge methodologies in

comparative and functional genomics, bioinformatics, proteomics,

evolutionary and population genetics, systems biology, epigenetics,

and biotechnology.

Cold Spring Harbor Laboratory Press is an internationally renowned

publisher of books, journals, and electronic media, located on Long

Island, New York. It is a division of Cold Spring Harbor Laboratory,

an innovator in life science research and the education of

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