An interesting study that provides another view of the relationship between accumulating damage, repair systems, and life span in cells: "Yeast cells, much like our own cells, have a finite ability to reproduce themselves. A 'mother' cell can only produce 20-30 'daughters' before it loses the ability to replicate and dies. ... Multidrug resistance (MDR) proteins are best known for helping cancer cells expel anticancer drugs - hence their name - but they also ferry compounds in and out of normal cells. [Researchers] found that yeast lacking certain MDR proteins have a shorter reproductive lifespan; they produce fewer daughter cells. Yeast engineered to contain more of these pumps, however, can produce more daughters. ... during division, the mother conserves damaged proteins and other cellular components that could prove harmful to the bud. ... Indeed, some research groups have posited that the mother's finite reproductive capability is the result of accumulating these damaged and toxic compounds. ... yeast division also results in an unequal distribution of MDR proteins. The mother cell retains the original MDR proteins while the bud gets young, newly formed MDR proteins. Because the mother's supply is never replenished, she has to rely on the pool of MDR proteins that she's born with. ... Over time these proteins decay. Some lose only part of their function; others may stop working altogether."

View the Article Under Discussion: http://www.nature.com/news/2010/100725/full/news.2010.373.html

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