Dynamics of mitochondria and mitochondrial DNA

Abstract

Mitochondria are dynamic organelles that fuse and divide. The study of mice lacking these dynamic processes has revealed physiological roles for mitochondrial dynamics. Recent studies indicate a link between mitochondrial dynamics and mitochondrial DNA (mtDNA) stability. To study this issue, we have performed structural studies on Tfam, a DNA binding protein that plays a central role in expression, maintenance, and organization of the mitochondrial genome. It activates transcription from mitochondrial promoters and organizes the mitochondrial genome into nucleoids. Using X-ray crystallography, we show that human Tfam forces promoter DNA to undergo a U-turn, reversing the direction of the DNA helix. The structural principles underlying DNA bending converge with those of the unrelated HU family proteins, which play analogous architectural roles in organizing bacterial nucleoids.

Additional details