The mRNA cap is a structure added to RNA pol II transcripts in eukaryotes, which recruits factors involved in RNA processing, nuclear export and translation initiation. RNMT-RAM, the mRNA cap methyltransferase complex, completes the basic functional mRNA cap structure, cap 0, by methylating the cap guanosine. Here we report that RNMT-RAM co-ordinates mRNA processing with ribosome production. Suppression of RNMT-RAM reduces synthesis of the 45S ribosomal RNA (rRNA) precursor. RNMT- RAM is required for c-Myc expression, a major regulator of RNA pol I, which synthesises 45S rRNA. Constitutive expression of c-Myc restores rRNA synthesis when RNMT-RAM is suppressed, indicating that RNMT-RAM controls rRNA production predominantly by controlling c-Myc expression. We report that RNMT-RAM is recruited to the rDNA locus, which may contribute to rRNA synthesis in certain contexts.
- mRNA cap