ИСТИНА

Cellular RNA has different chemical modifications, which are important for its biological function. m6A is one of the most abundant modifications in mRNA and non-coding RNAs [1]. Protein complex of two methyltransferases METTL3-METTL14 and supportive proteins performs m6A modification in human [2]. The U3 snoRNA is an abundant box C/D snoRNA that is required for the pre-rRNA processing and small ribosomal subunit assembly. We showed that METTL3 knockdown influence localization of U3 snoRNA in human cell. METTL3 knockdown resulted in accumulation of U3 in the cytoplasm at the expense of the reduction in nuclear localization. The dependence of U3 nuclear localization on METTL3 was confirmed by IP analysis using m6A antibody. It’s known that U3 snoRNA can shuttle between nucleus and cytoplasm. Early U3 monoparticles assemble in nucleoplasm or Cajal bodies and then imported to nucleolus for complete maturation [3]. So, we suggest that U3 maturation should involve METTL3 dependent methylation, which is necessary for the transport to nucleus/nucleolus.