2.1.1.309: 18S rRNA (guanine1575-N7)-methyltransferase
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For detailed information about 18S rRNA (guanine1575-N7)-methyltransferase, go to the full flat file.
Word Map on EC 2.1.1.309
Reaction
Synonyms
18S rRNA methyltransferase, BUD23, rRNA methyltransferase Bud23, WBSCR22, WBSCR22-TRMT112
ECTree
2.1.1.309 18S rRNA (guanine1575-N7)-methyltransferaseAdvanced search results
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General Information on EC 2.1.1.309 - 18S rRNA (guanine1575-N7)-methyltransferase
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GENERAL INFORMATION 
ORGANISM
UNIPROT
COMMENTARY 
LITERATURE
evolution
malfunction
metabolism
physiological function
additional information
Bud23 and Trm112 interact through formation of a beta-zipper involving main-chain atoms, burying an important hydrophobic surface and stabilizing the complex. The structures reveal that the coactivator Trm112 undergoes an induced fit to accommodate its methyltransferase (MTase) partner, identification of Bud23 residues important for Bud23-Trm112 complex formation and recruitment to pre-ribosomes
evolution
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Bud23 is a class I S-adenosyl-L-methionine (SAM)-dependent MTase
evolution
WBSCR22-TRMT112 is the functional homologue of Saccharomyces cerevisiae Bud23-Trm112
malfunction
deletion of BUD23 leads to severely impaired growth, reduced levels of the small (40S) ribosomal subunit, and a block in processing 20S rRNA to 18S rRNA, a late step in 40S maturation
malfunction
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trm112DELTA cells are deficient for Bud23-mediated 18S rRNA methylation at position G1575 and for small ribosome subunit formation. Bud23 failure to bind nascent preribosomes activates a nucleolar surveillance pathway involving the TRAMP complexes, leading to preribosome degradation
malfunction
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DELTAbud23 mutants have severely reduced small subunit levels and showa general failure in cleavage at site A2 during rRNA processing. A2 cleavage in a DELTAbud23 mutant is inefficient, with a marked reduction in the levels of 27S A2 intermediate. In the absence of A2 cleavage, cleavage at A3 is likely to be essential for separating the precursors for 40S and 60S processing. The strong negative genetic interaction observed between DELTAbud23 and RNase MRP components may reflect such a block in rRNA processing. Utp14 particle in a DELTAbud23 mutant contains U3 snoRNA but lacks 20S pre-rRNA. Phenotypes, overview. Although BUD23 is not essential for viability, deletion of the gene results in a severe slow-growth phenotype
malfunction
HeLa cells depleted of WBSCR22 show a mild reduction in 30S, indicative of reduced cleavage at site 2, and significant accumulation of 18S-E revealing inhibition of cleavage at site 3. Long and short truncated forms of 18S precursors are detected. On WBSCR22 depletion, the amount of mature 18S rRNA is markedly reduced and the 28S/18S rRNA ratio consequently increased. TRMT112 depletion leads to processing phenotypes largely similar to those observed upon WBSCR22 depletion (moderate 30S reduction and accumulation of 18S-E). The processing defects do not depend on p53 and are essentially the same, with minor differences, in different cell types. Kinetics of the pre-rRNA processing defects in HeLa cells by in vivo metabolic labeling, phenotype, overview
metabolism
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Bud23 failure to bind nascent preribosomes activates a nucleolar surveillance pathway involving the TRAMP complexes, leading to preribosome degradation
metabolism
DIMT1L, WBSCR22, and TRMT112 are required for distinct pre-rRNA processing steps, and the pre-rRNA processing defects are conserved in different cell types and do not depend on p53
physiological function
Bud23 protein, but not its methyltransferase activity, is important for biogenesis and export of the 40S subunit in yeast
physiological function
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Bud23 is responsible for the conserved methylation of G1575 of 18S rRNA, in the P-site of the small subunit of the ribosome. Bud23 protein, but not its methyltransferase activity, is important for its function. Bud23 is required for efficient A2 cleavage. Bud23 is required for the proper localization of small subunit components, UTP proteins mislocalize to the nucleoplasm in the absence of Bud23
physiological function
Bud23-Trm112 is required for efficient pre-rRNA processing steps leading to 18S rRNA synthesis and methylation of 18S rRNA at position G1575. Identification amd localization of Bud23Trm112 contacts with precursor ribosomes. The essential helicase Dhr1 interacts directly with Bud23-Trm112, proposing a concerted action of these proteins in ribosome assembly. The methyltransferase activity of Bud23-Trm112 is required for pre-rRNA processing are disconnected in time. Though Bud23-Trm112 binds precursor ribosomes at an early nucleolar stage, m7G methylation occurs at a late step of small subunit biogenesis, implying specifically delayed catalytic activation. Bud23-Trm112 interacts directly with the box C/D snoRNA U3-associated DEAH RNA helicase Dhr1 supposedly involved in central pseudoknot formation suggesting that Bud23-Trm112 might also contribute to controlling formation of this irreversible and dramatic structural reorganization essential to overall folding of small subunit rRNA. Formation of the Bud23-Trm112 complex is required for efficient 18S rRNA maturation
physiological function
the enzyme is required for distinct pre-rRNA processing reactions leading to synthesis of 18S rRNA. In human cells riboosome biogenesis requires the presence of the modification enzyme rather than its RNA-modifying catalytic activity. Methylation activity of WBSCR22-TRMT112 is not necessary for pre-rRNA processing
