Disease relevance of NAM2

• The purified protein cross-reacts with antibodies raised against the product of a LacZ/NAM2 gene fusion and antibodies raised against the purified Escherichia coli leucyl-tRNA synthetase [1].
• Here we show that Mycobacterium tuberculosis and human mitochondrial LeuRSs can substitute in splicing for the S. cerevisiae mitochondrial LeuRS [2].

High impact information on NAM2

• Dominant mutations in the yeast nuclear gene NAM2 cure the RNA splicing deficiency resulting from the inactivation of the bI4 maturase encoded by the fourth intron of the mitochondrial cytochrome b gene [3].
• This maturase is required to splice the fourth intron of this gene and to splice the fourth intron of the mitochondrial gene oxi3 encoding cytochrome oxidase subunit I. We have cloned the nuclear gene NAM2, which codes for two overlapping RNAs, 3.2 kb and 3.0 kb long, which are transcribed in the same direction but differ at their 5' ends [3].
• Inactivation of the NAM2 gene either by transplacement with a deleted copy of the gene, or by disruption, is not lethal to the cell, but leads to the destruction of the mitochondrial genome with the production of 100% cytoplasmic petites [3].
• NAM2 compensating mutations probably result from point mutations in the structural gene [3].
• Dominant mutations of the nuclear NAM2 gene are able to compensate for a deficiency of the maturase encoded by the fourth intron of the mitochondrial cytochrome b gene [4].

Biological context of NAM2

• This applies not only to the NAM2 coding regions, but also to two other ORFs flanking the NAM2 ORF [5].
• In addition to aminoacylation, LeuRS functions in RNA splicing [2].
• The structural gene (MSL1) coding for the mitochondrial enzyme has been cloned by transformation of two different G59 mutants with genomic libraries of wild type yeast nuclear DNA [6].

Anatomical context of NAM2

• We have purified the product of the NAM2 gene, the mitochondrial leucyl-tRNA synthetase, from yeast mitochondria [1].

Associations of NAM2 with chemical compounds

• The cytoplasmic LeuRS mRNA levels are induced by amino acid starvation resulting from the addition of aminotriazole [7].
• However, the mitochondrial LeuRS mRNA levels did increase dramatically upon inhibition of mitochondrial protein synthesis by chloramphenicol or ethidium bromide or in the temperature-sensitive strain leu-5 carrying a mutation in the mitochondrial LeuRS structural gene [7].

Physical interactions of NAM2

• Yeast mitochondrial leucyl-tRNA synthetase (LeuRS) binds to the bI4 intron and collaborates with the bI4 maturase to aid excision of the group I intron [8].

Enzymatic interactions of NAM2

• The cloned MSL1 gene was used to construct a strain in which 1 kb of the coding sequence was deleted and substituted with the yeast LEU2 gene [6].

Regulatory relationships of NAM2

• In each case, interactions with only the LeuRS protein fragment specifically stimulated bI4 intron splicing activity [8].

Analytical, diagnostic and therapeutic context of NAM2

• The association of ProRS with LeuRS was confirmed in vitro by native gel electrophoresis and size exclusion chromatography [9].

References