@article {430,
	title = {The Neurospora crassa cyt-20 gene encodes cytosolic and mitochondrial valyl-tRNA synthetases and may have a second function in addition to protein synthesis.},
	journal = {Mol Cell Biol},
	volume = {11},
	number = {8},
	year = {1991},
	month = {1991 Aug},
	pages = {4022-35},
	abstract = {The cyt-20-1 mutant of Neurospora crassa is a temperature-sensitive, cytochrome b- and aa3-deficient strain that is severely deficient in both mitochondrial and cytosolic protein synthesis (R.A. Collins, H. Bertrand, R.J. LaPolla, and A.M. Lambowitz, Mol. Gen. Genet. 177:73-84, 1979). We cloned the cyt-20+ gene by complementation of the cyt-20-1 mutation and found that it contains a 1,093-amino-acid open reading frame (ORF) that encodes both the cytosolic and mitochondrial valyl-tRNA synthetases (vaIRSs). A second mutation, un-3, which is allelic with cyt-20-1, also results in temperature-sensitive growth, but not in gross deficiencies in cytochromes b and aa3 or protein synthesis. The un-3 mutant had also been reported to have pleiotropic defects in cellular transport process, resulting in resistance to amino acid analogs (M.S. Kappy and R.L. Metzenberg, J. Bacteriol. 94:1629-1637, 1967), but this resistance phenotype is separable from the temperature sensitivity in crosses and may result from a mutation in a different gene. The 1,093-amino-acid ORF encoding vaIRSs is the site of missense mutations resulting in temperature sensitivity in both cyt-20-1 and un-3 and is required for the transformation of both mutants. The opposite strand of the cyt-20 gene encodes an overlapping ORF of 532 amino acids, which may also be functional but is not required for transformation of either mutant. The cyt-20-1 mutation in the vaIRS ORF results in severe deficiencies of both mitochondrial and cytosolic vaIRS activities, whereas the un-3 mutation does not appear to result in a deficiency of these activities or of mitochondrial or cytosolic protein synthesis sufficient to account for its temperature-sensitive growth. The phenotype of the un-3 mutant raises the possibility that the vaIRS ORF has a second function in addition to protein synthesis.},
	keywords = {Amino Acid Sequence, Base Sequence, Cloning, Molecular, Codon, Cosmids, Cytosol, DNA, Fungal, Genes, Bacterial, Mitochondria, Molecular Sequence Data, Neurospora crassa, Oligonucleotide Probes, Open Reading Frames, Phenotype, Plasmids, Restriction Mapping, Saccharomyces cerevisiae, Sequence Homology, Nucleic Acid, Valine-tRNA Ligase},
	issn = {0270-7306},
	author = {Kubelik, A R and Turcq, B and Lambowitz, A M}
}
