Scientists have figured why yeast cells, and maybe even other organisms' cells, are not able to go on producing copies of themselves forever.
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.
Rong Li and colleagues at the Stowers Institute for Medical Research in Kansas City, Missouri, 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.
Li and her colleagues found that 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, Li says.
Over time these proteins decay. Some lose only part of their function; others may stop working altogether.
We started to get the idea that "maybe these proteins are what's limiting the lifespan of these cells," Li says.
The team tested the idea that if the loss of MDR proteins does contribute to ageing, then cells that can't make these proteins should have shorter lifespans.