How RNA Is Shuttled into Mitochondria

Organelles called mitochondria are oftentimes referred to as the “power plants of the cell.” They are responsible for converting nutrients into ATP (adenosine triphosphate), the basic energy currency in all complex organisms. The mitochondrial genome is therefore extremely important, as is its replication, transcription and translation patterns. Small, nucleus-encoded RNA molecules are essential for all of these stages, and now researchers discovered how these molecules are shuttled into the mitochondria.

An essential cell protein called polynucleotide phosphorylase (PNPASE) is apparently responsible for this shuttling, experts at the University of California in Los Angeles (UCLA) say. They explain that shedding more light on the mechanisms that allow for RNA to penetrate mitochondria has been a goal in molecular biology for many years. They add that their study method proved successful where other failed. The new discovery was made by UCLA experts at the Jonsson Comprehensive Cancer Center, the Department of Chemistry and Biochemistry, and the Department of Pathology and Laboratory Medicine.

“This discovery tells us that PNPASE regulates the energy producing function of mitochondria by mediating cytoplasmic RNA import. The study yields new insight for how cells function at a very fundamental level. This information provides a potential new pathway to control mitochondrial energy production and possibly impact the growth of cells, including certain types of cancer cells,” says Jonsson Cancer Center researcher Dr. Michael Teitell. He is also the co-senior author of the new investigation, as well as a professor of pathology and laboratory medicine at the university. A paper accompanying the findings appears in the August 5 issue of the peer-reviewed medical journal Cell.

“When we're talking about looking for ways to cure cancer, we fundamentally need to understand what makes cells grow and die, and the mitochondrion is right at the heart of these issues. This new and novel pathway for transporting RNA into the mitochondria is shedding new light on the evolving role and importance of mitochondria function in normal physiology and a wide variety of diseases. If we can understand how this pathway functions in healthy cells, we could potentially uncover defects that help in transforming normal cells into cancer cells,” concludes Karla Koehler, the other co-senior author of the study, and a UCLA professor of chemistry and biochemistry.