S-adenosyl-L-methionine-dependent methyltransferase that has the ability to methylate both RNAs and proteins. Involved in pre-rRNA processing by catalyzing the site-specific 2'-hydroxyl methylation of ribose moieties in pre-ribosomal RNA. Probably catalyzes 2'-O-methylation of U6 snRNAs in box C/D RNP complexes. U6 snRNA 2'-O-methylation is required for mRNA splicing fidelity. Also acts as a protein methyltransferase by mediating methylation of 'Gln-105' of histone H2A (H2AQ104me), a modification that impairs binding of the FACT complex and is specifically present at 35S ribosomal DNA locus. L-glutaminyl-[histone H2A] + S-adenosyl-L-methionine = H(+) + N(5)-methyl-L-glutaminyl-[histone H2A] + S-adenosyl-L-homocysteine a ribonucleotide in rRNA + S-adenosyl-L-methionine = a 2'-O-methylribonucleotide in rRNA + H(+) + S-adenosyl-L-homocysteine a ribonucleotide in U6 snRNA + S-adenosyl-L-methionine = a 2'-O-methylribonucleotide in U6 snRNA + H(+) + S-adenosyl-L-homocysteine Component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles. Fibrillar region of the nucleolus. By homology to other fibrillarins, some or all of the N-terminal domain arginines are modified to asymmetric dimethylarginine (DMA). Belongs to the methyltransferase superfamily. Fibrillarin family.