How does RNA enter the cell’s mitochondria to initiate the production of energy? Researchers at the University of California Los Angeles, USA, have unravelled the mystery: A protein named polynucleotide phosphorylase (PNPase) transports RNA from the cytoplasm into the energy-producing power plants.

The macromolecule PNPase is located between the inner and outer membrane of the mitochondria. It binds RNA molecules in the cytoplasm and mediates their way into the matrix. When Geng Wang and his colleagues reduced the expression of PNPase, the RNA import into the mitochondria decreased. As a result, the cell could not produce the proteins required for the electron transport chain leading to stalled cell growth.

The findings could have implications for treating diseases: Cancer cells strongly rely on their energy supply to grow quickly and divide often.

• PNPASE Regulates RNA Import into Mitochondria
  G. Wang, H.-W. Chen, Y. Oktay, J. Zhang, E. L. Allen et al.,
  Cell 2010, 142(3), 456 – 467.
  DOI: 10.1016/j.cell.2010.06.035