Disease relevance of miaA

• The miaA mutator phenotype of Escherichia coli K-12 requires recombination functions [1].
• Effects of mutations in the Pseudomonas putida miaA gene: regulation of the trpE and trpGDC operons in P. putida by attenuation [2].
• Mutation of the miaA gene of Agrobacterium tumefaciens results in reduced vir gene expression [3].
• The wild-type miaA gene was cloned by selecting for lambda recombinant bacteriophage which eliminated the streptomycin-dependent phenotype and was subsequently recloned into plasmid vectors [4].

High impact information on miaA

• The pheS,T operon is also derepressed in strains carrying a trpX mutation [5].
• We show that the miaA mutator phenotype is dependent on recombination functions similar to, but not exactly the same as, those required for translation stress-induced mutagenesis [1].
• Both the mutant isolated in this work and previously isolated miaA mutants confer tetracycline sensitivity in the presence of functional Tet(M), both share a slow growth phenotype, and in neither case is a wild-type phenotype restored in trans by F'112 carrying the 89- to 98-min region of the chromosome [6].
• The function of the homologous gene in A. tumefaciens was proven by genetic complementation of E. coli miaA mutant strains. tRNA undermodification in A. tumefaciens miaA mutant strains may reduce vir gene expression by causing a reduced translation efficiency [3].
• Insertions in miaA cause exclusively GC----TA transversions, which contrasts with the GC----AT and AT----GC transitions observed in mutL mutants [7].

Chemical compound and disease context of miaA

• Tn5 insertion mutants defective in regulation of the Pseudomonas putida trpE and trpGDC operons by tryptophan were found to contain insertions in the P. putida miaA gene, whose product (in Escherichia coli) modifies tRNA(Trp) and is required for attenuation [2].
• Molecular cloning of the Escherichia coli miaA gene involved in the formation of delta 2-isopentenyl adenosine in tRNA [4].

Biological context of miaA

• miaA mutants, which contain A-37 instead of the ms(2)i(6)A-37 hypermodification in their tRNA, show a moderate mutator phenotype leading to increased GC-->TA transversion [1].
• This structural arrangement confirms that miaA and mutL are in the same complex operon [7].
• Three additional relationships were demonstrated between mutagenesis and the miaA gene or ms2i6A tRNA modification [8].
• We speculate that miaD causes a decrease in ms2i6A-37 tRNA demodification or an increase in miaA gene expression but not at the level of operon transcription [7].
• The miaA tRNA modification gene was cloned and located by insertion mutagenesis and DNA sequence analysis [8].

Associations of miaA with chemical compounds

• First, miaA transcription was induced by 2-aminopurine [8].
• The miaA gene product, delta 2-isopentenylpyrophosphate transferase, shows extensive homology with the yeast MOD5 gene product, and both enzymes contain a substrate binding site found in farnysyl pyrophosphate synthetase and a conserved putative ATP/GTP binding site [7].
• A mutation in miaA (trpX), a gene known to be involved in attenuation in the tryptophan operon, was also shown to increase transcription of the pheA gene [9].

Other interactions of miaA

• Second, chromosomal miaA insertion mutations increased the spontaneous mutation frequency with a spectrum distinct from mutL mutations [8].
• Instead, ppGpp is found to interfere with transcriptional readthrough in a manner which is dependent on the rpsL224, miaA, as well as the rpoB mutations [10].

References