Researchers at the Johns Hopkins Kimmel Cancer Center have found a set of 'master switches' for adult blood stem cells that keep cells in their primitive state.

MicroRNA molecules, once thought to be cellular junk, are now known to switch off activity of the larger RNA strands, which allow assembly of the proteins, the study revealed.

"Stem cells are poised to make proteins essential for maturing into blood cells, but microRNAs keep them locked in their place," the study's author Curt Civin said in a press release.

The finding of the study is reported in the online edition of the Proceedings of the National Academy of Sciences.