May have a role in processing of pre-rRNA or in the assembly of rRNA into ribosomal subunits (By similarity). May be involved in epigenetic regulation of muscle differentiation through regulation of the activity of the histone-lysine N-methyltransferase Suv4-20. Increased trimethylation of 'Lys-20' of histone H4. Belongs to the FRG1 family.