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Phoenix666 writes:

Some cells just don't get the respect they deserve. In fact, most cells don't. Over 99 percent of the innumerable cells on our planet exist in a state of quiescence. Pick up a handful of soil: it contains thousands of microorganisms, almost every one of which would not grow if you placed it in a culture dish. These cells are metabolically active -- yes, alive -- but they are not dividing. And they will remain in a reproductively "quiet" state unless stimulated under specific conditions to re-enter the cell cycle and gear up to divide once again.

Some of our most important cells, in fact, are quiescent, including stem cells, cells of the adaptive immune system, and oocytes -- eggs that women can carry for decades before being activated through fertilization.
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Today in the journal Science, a team of biologists led by Robert A. Martienssen, Cold Spring Harbor Laboratory (CSHL) Professor and HHMI-GBMI Investigator, presents evidence supporting a theory that places in profound perspective a battle within all cells between mechanisms that prompt them to replicate their DNA and those that enable them to transcribe their DNA into RNA. "It's an inherent choice that has to be managed, and accounts for much of what our cellular machinery is doing at any given time," Martienssen says.

The evidence Martienssen's team reports today is the result of turning the spotlight, for a change, on that multitudinous silent cellular majority -- cells in the quiescent state. Postdoctoral investigator Benjamin Roche performed experiments demonstrating for the first time that most cells cannot survive in a quiescent state unless an epigenetic mechanism called RNA interference (RNAi) is up and running. RNAi and other epigenetic processes induce changes in where and when specific genes are expressed without altering their genetic code.

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