S-adenosyl-L-methionine-dependent methyltransferase that has the ability to methylate both RNAs and proteins (PubMed:32017896). Involved in pre-rRNA processing by catalyzing the site-specific 2'-hydroxyl methylation of ribose moieties in pre-ribosomal RNA (By similarity). Site specificity is provided by a guide RNA that base pairs with the substrate (By similarity). Methylation occurs at a characteristic distance from the sequence involved in base pairing with the guide RNA (By similarity). Probably catalyzes 2'-O-methylation of U6 snRNAs in box C/D RNP complexes (PubMed:32017896). U6 snRNA 2'-O-methylation is required for mRNA splicing fidelity (PubMed:32017896). 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 (By similarity). 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 that contain SNU13, FBL, NOP5 and NOP56, plus a guide RNA. It is associated with the U3, U8, U13, X and Y small nuclear RNAs. Component of several ribosomal and nucleolar protein complexes. Interacts with PRMT5 and UTP20. Interacts with DDX5 and C1QBP. Interacts with NOL11. Interacts with PIH1D1. Interacts with RRP1B (By similarity). Interacts with NOLC1 (By similarity). 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). Ubiquitinated. Ubiquitination leads to proteasomal degradation. Deubiquitinated by USP36. Acetylated by CREBBP/CBP, preventing methylation of 'Gln-105' of histone H2A (H2AQ104me), without affecting rRNA methylation. Deacetylation by SIRT7 restores methylation of 'Gln-105' of histone H2A (H2AQ104me). Belongs to the methyltransferase superfamily. Fibrillarin family.