The 18S rRNA dimethylase Dim1p is required for pre-ribosomal RNA processing in yeast

Denis Lafontaine*, Jean Vandenhaute, David Tollervey

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

The m2/6A1779m2/6A1780 dimethylation at the 3' end of the small subunit rRNA has been conserved in evolution from bacteria to eukaryotes. The yeast 18S rRNA dimethylase gene DIM1 was cloned previously by complementation in Escherichia coli and shown to be essential for viability in yeast. A conditional GAL10::dim1 strain was constructed to allow the depletion of Dim1p from the cell. During depletion, dimethylation of the pre- rRNA is progressively inhibited and pre-rRNA processing at cleavage sites A1 and A2 is concomitantly lost. In consequence, the mature 18S rRNA and its 20S precursor drastically underaccumulate. This has the effect of preventing the synthesis of nonmethylated rRNA. To test whether the processing defect is a consequence of the absence of the dimethylated nucleotides or of the Dim1p dimethylase itself, a cis-acting mutation was created in which both dimethylated adenosines are replaced by guanosine residues. Methylation cannot occur on this mutant pre-rRNA, but no clear pre-rRNA processing defect is seen. Moreover, methylation of the wild-type pre-rRNA predominantly occurs after cleavage at sites A1 and A2. This shows that formation of the m2/6A1779m2/6A1780 dimethylation is not required for pre-rRNA processing. We propose that the binding of Dim1p to the pre-ribosomal particle is monitored to ensure that only dimethylated pre-rRNA molecules are processed to 18S rRNA.

Original languageEnglish
Pages (from-to)2470-2481
Number of pages12
JournalGenes and Development
Volume9
Issue number20
DOIs
Publication statusPublished - 15 Oct 1995

Keywords / Materials (for Non-textual outputs)

  • methylation
  • ribosome synthesis
  • RNA processing
  • rRNA
  • yeast

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