Genetics, Vol. 159, 147-157, September 2001, Copyright © 2001
Regulation of Physiological Rates in Caenorhabditis elegans by a tRNA-Modifying Enzyme in the Mitochondria
Jason Lemieuxa,
Bernard Lakowskia,
Ashley Webba,
Yan Menga,
Antonio Ubacha,
Frédéric Bussièrea,
Thomas Barnesa, and
Siegfried Hekimia
a Department of Biology, McGill University, Montréal, Québec H3A 1B1, Canada
Corresponding author:
Siegfried Hekimi, Department of Biology, McGill University, 1205 Ave. Dr. Penfield, Montréal, Québec H3A 1B1, Canada., siegfried.hekimi{at}mcgill.ca (E-mail)
Communicating editor: P. ANDERSON
We show that the phenotype associated with gro-1(e2400) comprises the whole suite of features that characterize the phenotype of the clk mutants in Caenorhabditis elegans, including deregulated developmental, behavioral, and reproductive rates, as well as increased life span and a maternal effect. We cloned gro-1 and found that it encodes a highly conserved cellular enzyme, isopentenylpyrophosphate:tRNA transferase (IPT), which modifies a subset of tRNAs. In yeast, two forms of the enzyme are produced by alternative translation initiation, one of which is mitochondrial. In the gro-1 transcript there are also two possible initiator ATGs, between which there is a sequence predicted to encode a mitochondrial localization signal. A functional GRO-1::GFP fusion protein is localized diffusely throughout the cytoplasm and nucleus. A GRO-1::GFP initiated from the first methionine is localized exclusively to the mitochondria and rescues the mutant phenotype. In contrast, a protein initiated from the second methionine is localized diffusely throughout the cell and does not rescue the mutant phenotype. As oxygen consumption and ATP concentration have been reported to be unaffected in gro-1 mutants, our observations suggest that GRO-1 acts in mitochondria and regulates global physiology by unknown mechanisms.
