Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Modified nucleosides in tRNAs play important roles in tRNA structure, biosynthesis and function, and serve as crucial determinants of bacterial growth and virulence. In the yeast Saccharomyces cerevisiae, mutants defective in N1-methylation of a highly conserved adenosine (A58) in the TPsiC loop of initiator tRNA are non-viable. The yeast m1A58 methyltransferase is a heterotetramer consisting of two different polypeptide chains, Gcd14p and Gcd10p. Interestingly, while m1A58 is not found in most eubacteria, the mycobacterial tRNAs have m1A58. Here, we report on the cloning, overexpression, purification and biochemical characterization of the Rv2118c gene-encoded protein (Rv2118p) from Mycobacterium tuberculosis, which is homologous to yeast Gcd14p. We show that Rv2118c codes for a protein of approximately 31 kDa. Activity assays, modified base analysis and primer extension experiments using reverse transcriptase reveal that Rv2118p is an S-adenosyl-l-methionine-dependent methyltransferase which carries out m1A58 modification in tRNAs, both in vivo and in vitro. Remarkably, when expressed in Escherichia coli, the enzyme methylates the endogenous E.coli initiator tRNA essentially quantitatively. Furthermore, unlike its eukaryotic counterpart, which is a heterotetramer, the mycobacterial enzyme is a homotetramer. Also, the presence of rT modification at position 54, which was found to inhibit the Tetrahymena pyriformis enzyme, does not affect the activity of Rv2118p. Thus, the mycobacterial m1A58 tRNA methyltransferase possesses distinct biochemical properties. We discuss aspects of the biological relevance of Rv2118p in M.tuberculosis, and its potential use as a drug target to control the growth of mycobacteria.
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PMID:Mycobacterium tuberculosis Rv2118c codes for a single-component homotetrameric m1A58 tRNA methyltransferase. 1496 Jul 15

Following synthesis, RNA can be modified with over 100 chemically distinct modifications. Recently, two studies-one by our group-developed conceptually similar approaches to globally map N1-methyladenosine (m1A) at single nucleotide resolution. Surprisingly, the studies diverged quite substantially in their estimates of the abundance, whereabouts, and stoichiometry of m1A within internal sites in cytosolic mRNAs: One study reported it to be a very rare modification, present at very low stoichiometries, and invariably catalyzed by TRMT6/61A. The other found it to be present at >470 sites, often at high levels, and suggested that the vast majority were highly unlikely to be TRMT6/61A substrates. Here we reanalyze the data from the latter study, and demonstrate that the vast majority of the detected sites originate from duplications, misannotations, mismapping, SNPs, sequencing errors, and a set of sites from the very first transcribed base that appear to originate from nontemplated incorporations by reverse transcriptase. Only 53 of the sites detected in the latter study likely reflect bona-fide internal modifications of cytoplasmically encoded mRNA molecules, nearly all of which are likely TRMT6/TRMT61A substrates and typically modified at low to undetectable levels. The experimental data sets from both studies thus consistently demonstrate that within cytosolic mRNAs, m1A is a rare internal modification where it is typically catalyzed at very low stoichiometries via a single complex. Our findings offer a clear and consistent view on the abundance and whereabouts of m1A, and lay out directions for future studies.
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PMID:m1A within cytoplasmic mRNAs at single nucleotide resolution: a reconciled transcriptome-wide map. 3013 2