Division of mitochondria requires a novel DNM1-interacting protein, net2p

Mitochondria are dynamic organelles that undergo frequent division and fusi on, but the molecular mechanisms of these two events are not well understoo d. Dnm1p, a mitochondria-associated, dynamin-related GTPase was previously shown to mediate mitochondrial fission. Recently, a genome-wide yeast two-h ybrid screen identified an uncharacterized protein that interacts with Dnm1 p. Cells disrupted in this new gene, which we call NET2, contain a single m itochondrion that consists of a network formed by interconnected tubules, s imilar, to the phenotype of dnm1 Delta cells. NET2 encodes a mitochondria-a ssociated protein with a predicted coiled-coil region and six WD-40 repeats . Immunofluorescence microscopy indicates that Net2p is located in distinct , dot-like structures along the mitochondrial surface, many of which coloca lize with the Dnm1 protein. Fluorescence and immunoelectron microscopy show s that Dnm1p and Net2p preferentially colocalize at constriction sites alon g mitochondrial tubules. Our results suggest that Net2p is a new component of the mitochondrial division machinery.