EC Number |
General Information |
Reference |
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2.1.1.216 | evolution |
Trm1 enzymes can be divided into two types on the basis of their specificity for the target guanosine(s). One is a single-site-specific, which modifies only G26 and is found in eukaryotes and archaea. The second is a multi-site-specific Trm1, which modifies both G26 and G27 and is found in the hyperthermophilic eubacterium, Aquifex aeolicus |
-, 756985 |
2.1.1.216 | malfunction |
little changes occur in the relative levels of different tRNAs in maf1DELTA cells. By contrast, the efficiency of N2,N2-dimethyl G26 modification on certain tRNAs is decreased in response to maf1-deletion and is associated with antisuppression |
737063 |
2.1.1.216 | malfunction |
treatment with rapamycin or overexpression of maf1+ reduces tRNA transcription with increase in the m22G26 content of sup-tRNASerUCA and its specific activity for suppression. Mutations in a catalytic subunit of RNAP III associated with hypomyelinating leukodystrophy (HLD) to show that a general decrease in tRNA transcription by another mechanism also increases m22G26 modification efficiency and reverses antisuppression in Schizosaccharomyces pombe. G26 misincorporations are decreased to below 1% in trm1DELTA mutant cells. Expression of trm1+ from a high copy plasmid in trm1DELTA cells restores the misincorporations to higher levels than in wild-type cells |
-, 758108 |
2.1.1.216 | metabolism |
global tRNA gene activation occurs with derepression of RNA polymerase III via maf1-deletion and is accompanied by a paradoxical loss of tRNA-mediated nonsense suppressor activity, manifested as an antisuppression phenotype. maf1-Antisuppression also occurs in the fission yeast amidst general activation of RNA polymerase III. Dimethyl-guanine-26 varies in the efficiency by which it is added to its target tRNAs, in a manner that is dependent on the overall activity rate of RNA polyymerase III. Overexpression of Trm1, which produces the N2,N2-dimethyl G26 modification, reverses maf1-antisuppression. Competition by increased tRNA levels in maf1DELTA cells leads to N2,N2-dimethyl G26 hypomodification due to limiting Trm1, reducing the activity of suppressor-tRNASerUCA and accounting for antisuppression |
737063 |
2.1.1.216 | metabolism |
the tRNA modification dimethyl-guanine-26 (m22G26) varies in the efficiency by which it is added to its target tRNAs, in a manner that is dependent on the overall activity rate of RNA polymerase III (RNAP III) that synthesizes the tRNAs. Rapamycin decreases tRNA synthesis in a maf1+-dependent manner in Schizosaccharomyces pombe. Hypomodification of m22G26 is responsible for maf1DELTA antisuppression. RNAP III mutations that decrease tRNA synthesis also increase m22G26 efficiency and tRNA activity |
-, 758108 |
2.1.1.216 | physiological function |
after their synthesis by RNAP III, tRNAs are chemically modified by enzymes on multiple of their nucleosides, also involving the enzyme. G26 is modified by N2,N2 dimethylation (m2 2G26) in many tRNAs by the Trm1 methyltransferase. Trm1 is a nuclear enzyme that produces m2 2G26 which likely contributes to proper tRNA folding. N2,N2-dimethyl G26 (m22G26) can enhance tRNA function. Trm1 activity is limiting in the context of increased tRNA production in maf1DELTA cells and its overexpression reverses antisuppression. Of the 36 tRNAs in Schizosaccharomyces pombe that have G26, 27 show significant misincorporation at G26. The extent of G26 misincorporation varies with tRNA identity from 10-80%, G26 misincorporations are due to m22G26 modification. A significant amount of Trm1 substrates are not fully modified in wild-type cells because Trm1 activity is limiting. Hypomodification of m22G26 is responsible for maf1DELTA antisuppression. m22G26 modification debilitates normal base pairing. Efficiency of m22G26 modification responds to growth/nutrient conditions, overview |
-, 758108 |
2.1.1.216 | physiological function |
initiator tRNAMet from Thermoplasma acidophilum contains the m22G26 modification in addition to m2G26, the TrmI activity is responsible for these modifications |
729858 |
2.1.1.216 | physiological function |
the N2,N2-dimethyl G26 modification activates the tRNA for function to translate the code. The N2,N2-dimethyl G26 modification is required for the suppressor activity of sup-tRNASerUCA. The enzyme activity is regulated by nutrient/growth conditions |
737063 |
2.1.1.216 | physiological function |
the Ta0997 gene product methylates the tRNALeuUAG transcript and 14C-nucleotide analysis reveals that the modified nucleotide is pm22G. Archaeal Trm1 can methylate the tRNALeuUAG transcript, which has a long variable region. In the case of class I tRNAs, archaeal Trm1 is reported to recognize the D-stem and the size of the variable region. Therefore, archaeal Trm1 might be able to recognize the large variable region in the class II tRNAs. Trm1 efficiently methylates both the mature elongator tRNAMet transcript and the precursor with an intron. Archaeal Trm1 does not recognize the anticodon loop. The G modification at position 26 is a mixture of m2G and m22G, which is formed by Trm1 |
-, 756985 |