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.