Genetic tradeoff: Harmful genes are widespread in yeast but hold hidden benefits

http://www.eurekalert.org/pub_releases/2012-10/uom-gth102312.php

Public release date: 25-Oct-2012
Contact: Jim Erickson
University of Michigan

ANN ARBOR— The genes responsible for inherited diseases are clearly bad for us, so why hasn't evolution, over time, weeded them out and eliminated them from the human genome altogether? Part of the reason seems to be that genes that can harm us at one stage of our lives are necessary and beneficial to us at other points in our development.

The idea that the same gene can be both beneficial and harmful, depending on the situation, is called antagonistic pleiotropy. The theory has been around since the 1950s and has been used to explain aging, cancer and genetic diseases.

But until now, no one has been able to determine just how common antagonistic pleiotropy is -- on a genome-wide scale -- in any organism. In a paper to be published online Oct. 25 in the journal Cell Reports, Jianzhi "George" Zhang of the University of Michigan and his coworkers report that antagonistic pleiotropy is very common in yeast, a single-celled organism used by scientists to provide insights about genetics and cell biology.

Zhang and his colleagues say the findings have broad biomedical and evolutionary implications.

"In any given environment, yeast expresses hundreds of genes that harm rather than benefit the organism, demonstrating widespread antagonistic pleiotropy. The surprising finding is the sheer number of such genes in the yeast genome that have such properties," said Zhang, a professor in the Department of Ecology and Evolutionary Biology.

"From our yeast data we can predict that humans should have even more antagonistic pleiotropy than yeast," he said. "This suggests that special cautions are needed when treating inherited diseases, because a treatment that removes a disease-causing genetic effect may lead to adverse effects in other aspects of life."

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