S-adenosyl-L-methionine-dependent methyltransferase that has the ability to methylate both RNAs and proteins (Probable). Involved in pre-rRNA processing. Utilizes the methyl donor S-adenosyl-L-methionine to catalyze the site-specific 2'-hydroxyl methylation of ribose moieties in pre-ribosomal RNA (Probable). Site specificity is provided by a guide RNA that base pairs with the substrate (Probable). Methylation occurs at a characteristic distance from the sequence involved in base pairing with the guide RNA (Probable). Also acts as a protein methyltransferase by mediating methylation of 'Gln-105' of histone H2A (H2AQ105me), a modification that impairs binding of the FACT complex and is specifically present at 35S ribosomal DNA locus (By similarity). Acts as negative regulator of expression of immune responsive genes, including pathogenesis-related gene 1 (PR1), and of resistance against bacterial pathogen (PubMed:30307032). Binds to MED19A, a positive regulator of PR1 expression, to repress the activator activity of MED19A (PubMed:30307032). In response to the bacterial pathogen-associated molecular pattern (PAMP) elf18, associates with the long non-coding RNA (lncRNA) ELENA1 (At4g16355), and releases its repression of MED19A (PubMed:30307032). Possesses ribonuclease activity toward rRNA in vitro (PubMed:29163603). Binds phosphoinositides, phospholipids and phosphatidic acid in vitro (PubMed:29163603). a ribonucleotide in rRNA + S-adenosyl-L-methionine = a 2'-O-methylribonucleotide in rRNA + H(+) + S-adenosyl-L-homocysteine L-glutaminyl-[histone H2A] + S-adenosyl-L-methionine = H(+) + N(5)-methyl-L-glutaminyl-[histone H2A] + S-adenosyl-L-homocysteine Component of box C/D small nucleolar ribonucleoprotein (snoRNP) particles (By similarity). Interacts with groundnut rosette virus long-distance movement protein; this interaction is required for virus long-distance movement protein transiting through host Cajal body and nucleolus, relocalization of fibrillarin to the cytoplasm, and in presence of viral RNA, leads to the formation of stable RNPs (PubMed:17576925). Interacts (via GAR domain) with the hordeivirus TGB1 movement protein (via the first 82 amino acid residues) (PubMed:22349738). Interacts with PRMT11 and PRMT12 (PubMed:17666011). Interacts with MED19A (PubMed:30307032). Localizes to the fibrillar region of the nucleolus. Expressed in roots and flowers (PubMed:10829025, PubMed:10806224). Expressed in leaves and stems (PubMed:10806224). Expression levels decrease during aging (PubMed:10806224). Repressed by abscisic acid (ABA). The N-terminal DMA/Gly-rich region (also called GAR domain) is rich in Gly and Arg and functions in nucleolar targeting (By similarity). The central (138-179) and C-terminal (225-281) part of the protein exhibit cooperative RNA-binding activities. Methylated by PRMT11 and PRMT12. Baeckstroem et al identified FIB2 in a Mediator complex pull-down assay and suggested that FIB2 could be a plant specific component of the Mediator complex (PubMed:17560376). However, no experimental evidence has been brought so far to confirm this hypothesis (Probable). Belongs to the methyltransferase superfamily. Fibrillarin family.